Question

evaluate the validity of this statement.
a it is an valid statement. stars produce energy by a fusion chain reaction of hydrogen into helium.
b it is an invalid statement. stars produce energy by a fusion chain reaction of hydrogen into helium.
c it is an invalid statement. stars produce energy by a fission chain reaction of hydrogen into helium.
d it is an valid statement. stars produce energy by fission and fusion chain reactions of hydrogen into helium and vice versa.

Explanation:

Step1: Analyze fusion and fission

Fusion combines light nuclei (e.g., hydrogen to helium), fission splits heavy nuclei.

Step2: Check star energy production

Stars use hydrogen - to - helium fusion. Chain reaction in stars is fusion (proton - proton chain or CNO cycle), not fission. So statement in A (valid) is wrong as it's just fusion (not chain reaction in the sense of a self - sustaining, rapidly multiplying reaction like in nuclear bombs; in stars, it's a controlled fusion process). Statement in B: Stars do fusion (correct process), but the term “chain reaction” is misused here (in stars, it's a series of fusion steps but not a “chain reaction” as in a runaway fission - like chain). However, compared to other options:

• Option C: Fission is wrong for stars.
• Option D: Fission is wrong and “vice versa” (helium to hydrogen) is not the main energy - producing process in stars. So B is the most appropriate among the given options considering the process (fusion) is correct but the “chain reaction” description is a bit off (but less wrong than others).

Answer:

B. It is an invalid statement. Stars produce energy by a fusion chain reaction of hydrogen into helium.