Question

a fusion reaction takes place between carbon and another element. neutrons are released, and a different element is formed. the different element is lighter than helium. heavier than helium. used for energy on earth. radioactive.

Explanation:

1. First, recall what nuclear fusion is: combining lighter atomic nuclei to form a heavier nucleus. Carbon has an atomic mass greater than helium (helium has an atomic mass of ~4, carbon is ~12). When carbon fuses with another element, the resulting element should be heavier than the reactants (or at least, since carbon is already heavier than helium, the product will be heavier than helium).

• Option 1: Lighter than helium is wrong because carbon is heavier than helium, and fusion of carbon with another element would make a heavier element, not lighter than helium.
• Option 3: Fusion for energy on Earth is mainly hydrogen (like in the sun, but on Earth, we don't use carbon fusion for energy currently, and the question is about the element formed, not its use for energy.
• Option 4: Not all fusion products are radioactive, and this isn't a defining characteristic here.
• Option 2: Since carbon (atomic mass ~12) fuses with another element, the product will have a higher atomic mass than carbon (or at least, since carbon is heavier than helium, the product is heavier than helium).

Answer:

B. heavier than helium