1. The tiny contractile units within muscle cells are called:

A. Myocytes
B. Myofibrils
C. Sarcomeres
D. Tendons

Correct answer: C

Rationale: The correct answer is C: Sarcomeres. Sarcomeres are the basic contractile units within muscle cells. They are made up of overlapping filaments of actin and myosin proteins, which slide past each other during muscle contraction, resulting in muscle movement. Myocytes (A) are muscle cells, myofibrils (B) are cylindrical structures within muscle fibers composed of sarcomeres, and tendons (D) are tough bands of connective tissue that connect muscle to bone. Therefore, sarcomeres are specifically responsible for muscle contraction within muscle cells.

2. 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.

3. The final sentence suggests that users should approach social media with a healthy dose of

A. Enthusiasm and optimism about its potential for connection and engagement.
B. Skepticism and critical thinking towards the information encountered online.
C. Acceptance of its flaws and a passive reliance on its features for interaction.
D. Indifference towards its impacts and an absence of any effort to manage its use.

Correct answer: B

Rationale: The emphasis on "critical thinking" and "skepticism" suggests the importance of approaching social media with a cautious and discerning mind, aligning with B

4. What type of bond involves the complete transfer of electrons between atoms?

A. Covalent bond
B. Ionic bond
C. Metallic bond
D. Hydrogen bond

Correct answer: B

Rationale: Ionic bond - Electrons are completely transferred from one atom to another, creating cations and anions with strong electrostatic attraction.

5. What is the difference between active and passive immunity?

A. Active immunity is short-lived, while passive immunity is long-lasting.
B. Active immunity involves the body's own immune response, while passive immunity provides immediate protection through antibodies from another source.
C. Active immunity only protects against bacterial infections, while passive immunity works against both bacteria and viruses.
D. Passive immunity requires repeated vaccinations, while active immunity is a one-time process.

Correct answer: A

Rationale: The correct answer is A: "Active immunity involves the body's own immune response, while passive immunity provides immediate protection through antibodies from another source." Active immunity is long-lasting because it involves the body's immune system producing memory cells that remember specific pathogens, providing long-term protection. Passive immunity, on the other hand, is short-lived as it involves receiving pre-formed antibodies from an external source, such as through maternal transfer or injection of antibodies, which do not create memory cells for long-lasting protection.

6. The least common multiple (LCM) of two numbers is the smallest number that is a multiple of both. Which of the following represents the LCM of 14 and 21?

A. 42
B. 63
C. 84
D. 168

Correct answer: C

Rationale: We can list out the multiples of each number until we find a common multiple. 14, 28, 42, 56, 84, ... 21, 42, 63, 84, ... The least common multiple is 84.