What is TRUE about carbon-13 and carbon-14?
a) They are isotopes.
b) They have the same mass number.
c) They have the same number of neutrons in their nuclei.
d) They behave differently in biological reactions.
e) None of the above are true.

• A. They are isotopes.
• B. They have the same mass number.
• C. They have the same number of neutrons in their nuclei.
• D. They behave differently in biological reactions.
• E. None of the above are true.

Answer: (A)

Verified step by step guidance

1. Understand the concept of isotopes: Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means they have different mass numbers.
2. Identify the atomic number of carbon: Carbon has an atomic number of 6, which means it has 6 protons.
3. Determine the number of neutrons in carbon-13 and carbon-14: Carbon-13 has 7 neutrons (13 - 6 = 7) and carbon-14 has 8 neutrons (14 - 6 = 8).
4. Evaluate the mass number: The mass number is the sum of protons and neutrons. Carbon-13 and carbon-14 have different mass numbers (13 and 14, respectively).
5. Consider their behavior in biological reactions: Isotopes can behave differently in biological reactions due to their mass differences, but this is not always the case for all isotopes.