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What type of muscle tissue is responsible for causing the hair follicles to stand on end when you get a goosebump?
- A. Skeletal muscle
- B. Smooth muscle
- C. Cardiac muscle
- D. None of the above
Correct Answer: B
Rationale: Smooth muscle is responsible for causing the hair follicles to stand on end when you get a goosebump. This type of muscle tissue is found in the skin attached to hair follicles and contracts in response to stimuli such as cold or fear, causing the hair to stand up. Skeletal muscle is responsible for voluntary movements, and cardiac muscle is found in the heart and is not directly involved in causing goosebumps. Therefore, choices A, C, and D are incorrect as they do not represent the specific type of muscle tissue responsible for this physiological response.
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What is the net force acting on a car traveling at a constant speed on a straight road?
- A. A force equal to its weight pushing upwards
- B. A force equal to its weight pushing downwards
- C. A force equal to its engine power pushing forward
- D. No net force
Correct Answer: D
Rationale: When a car is traveling at a constant speed on a straight road, it indicates that the forces acting on the car are balanced. In this scenario, there is no acceleration or deceleration, meaning the net force on the car is zero. If there was a net force present, it would cause the car to either accelerate or decelerate. Choices A, B, and C are incorrect because in a situation where a car is moving at a constant speed, the forces are balanced, and there is no unbalanced force acting in any specific direction.
What is the shape of the DNA molecule?
- A. Linear
- B. Circular
- C. Double helix
- D. Straight chain
Correct Answer: C
Rationale: The correct answer is C: Double helix. The shape of the DNA molecule is a double helix, a structure first described by James Watson and Francis Crick in 1953. This shape consists of two strands twisted around each other in a spiral. The double helix structure allows DNA to be compactly stored within the cell nucleus and provides stability to the molecule. Options (A) Linear, (B) Circular, and (D) Straight chain are incorrect as they do not accurately represent the shape of the DNA molecule. DNA is not linear but rather forms a twisted double helix; it is not circular like a ring but has a spiral structure, and it is not a straight chain but a twisted ladder-like structure.
When is work done on an object?
- A. Only when the object's velocity changes
- B. Only when a force is applied to the object
- C. Whenever there is a force exerted on the object causing displacement
- D. Only when the object is lifted vertically
Correct Answer: C
Rationale: Work is done on an object whenever a force causes displacement in the object's position. According to the work-energy principle, work is calculated as the force applied multiplied by the distance the object moves in the direction of the force. Therefore, work can occur whenever there is a force exerted on the object resulting in displacement, regardless of whether the object's velocity changes or it is lifted vertically. Choice A is incorrect because work can be done even without a change in velocity. Choice B is incorrect as work requires both force and displacement, not just the application of force. Choice D is incorrect because work is not limited to vertical lifting; it can happen in any direction as long as there is a force causing displacement.
The Gram stain is a differential staining technique used to classify bacteria based on their cell wall composition. Gram-positive bacteria appear
- A. Pink
- B. Blue
- C. Red
- D. Purple
Correct Answer: D
Rationale: The Gram stain is a differential staining technique that categorizes bacteria into two groups based on their cell wall composition: Gram-positive and Gram-negative. Gram-positive bacteria have a thick layer of peptidoglycan in their cell walls, which retains the crystal violet stain used in the Gram staining procedure. Consequently, Gram-positive bacteria appear purple under the microscope after staining. On the other hand, Gram-negative bacteria possess a thinner peptidoglycan layer and an outer membrane that can be penetrated by the counterstain safranin, leading them to appear pink or red. Blue is not typically used to describe the color of bacteria in a Gram stain, making it an incorrect choice.
What is the valve that prevents blood from flowing back from the left ventricle into the left atrium?
- A. Tricuspid valve
- B. Mitral valve
- C. Aortic valve
- D. Pulmonic valve
Correct Answer: B
Rationale: The correct answer is the Mitral valve. The mitral valve is located between the left atrium and the left ventricle of the heart. Its function is to prevent the backflow of blood from the left ventricle into the left atrium during ventricular contraction. Choice A, the Tricuspid valve, is incorrect as it is located between the right atrium and right ventricle. Choice C, the Aortic valve, and Choice D, the Pulmonic valve, are also incorrect as they are involved in the circulation of blood leaving the heart rather than preventing backflow within the atria and ventricles.