1. Vaccines work by stimulating the immune system to develop:

A. A physical barrier against pathogens
B. An inflammatory response
C. Immunological memory to a specific pathogen
D. Phagocytes to engulf pathogens

Correct answer: C

Rationale: The correct answer is C: 'Immunological memory to a specific pathogen.' Vaccines work by introducing a harmless form of a pathogen or a piece of it to stimulate the immune system. This exposure triggers the production of antibodies and memory cells specific to that pathogen. These memory cells 'remember' the pathogen, allowing the immune system to respond more effectively and rapidly if exposed to the actual pathogen in the future. Options A, B, and D are incorrect because vaccines do not create a physical barrier, induce a general inflammatory response, or directly cause phagocytes to engulf pathogens; instead, vaccines enhance the immune system's ability to recognize and combat specific pathogens.

2. What type of force allows a car to take a sharp turn while moving in a circular path?

A. Centripetal force
B. Tension force
C. Frictional force
D. Gravitational force

Correct answer: A

Rationale: Centripetal force is the force that allows an object to move in a circular path. In the case of a car taking a sharp turn, the centripetal force is directed towards the center of the circle, keeping the car moving in a curved path. Tension force is the force transmitted through a string, rope, cable, or wire when it is pulled tight by forces acting from opposite ends. Frictional force opposes the motion of an object and is not the primary force responsible for allowing a car to take a sharp turn. Gravitational force is the force of attraction between two masses and is not directly related to a car taking a sharp turn.

3. What property of a wave is measured in Hertz (Hz)?

A. Amplitude
B. Wavelength
C. Speed
D. Frequency

Correct answer: d

Rationale: Frequency, the number of oscillations per second, is measured in Hertz (Hz).

4. 12 is a/an:

A. even number
B. odd number
C. prime number
D. composite number

Correct answer: A

Rationale: Even numbers are integers divisible by 2 without a remainder. Since 12 divided by 2 equals 6 with no remainder, 12 is even.

5. Which of the following types of muscle tissue is found attached to bones and allows for voluntary movement?

A. Smooth muscle
B. Cardiac muscle
C. Skeletal muscle
D. Connective tissue

Correct answer: C

Rationale: The correct answer is C: Skeletal muscle. Skeletal muscle is the type of muscle tissue that is attached to bones and allows for voluntary movement. This type of muscle is under conscious control, meaning we can choose to contract or relax these muscles to produce movement. Smooth muscle (option A) is found in the walls of internal organs and is not under voluntary control. Cardiac muscle (option B) is found in the heart and also functions involuntarily. Connective tissue (option D) primarily provides support and structure to the body but does not directly enable movement like skeletal muscle does.

6. Which of the following properties is NOT characteristic of a covalent bond?

A. Sharing of electrons between atoms
B. High melting and boiling points
C. Low electrical conductivity in solid state
D. Directional bonding

Correct answer: B

Rationale: Covalent bonds are formed by the sharing of electrons between atoms. This sharing results in the formation of molecules with directional bonding, where the atoms are held together in a specific orientation. Covalent compounds generally have low melting and boiling points compared to ionic compounds, as the intermolecular forces in covalent compounds are weaker. Additionally, covalent compounds do not conduct electricity in the solid state because the electrons are localized between the atoms and not free to move and carry charge.