Final answer:
During muscle contraction, the Z lines get closer together, the H zones get smaller, and the I band gets smaller, while the A band remains consistent in width. The correct changes are A, B, and C.
Step-by-step explanation:
When a muscle contracts, several changes occur within the structure of a sarcomere, which is the functional unit of a striated muscle. The following changes are observed:
- The Z lines, which define the boundaries of each sarcomere, get closer together (A).
- The H zones, which are the central regions of the A band containing only thick filaments, get smaller (B).
- The I band, which contains only thin filaments, gets smaller (C).
- The A band, which contains the entire length of thick filaments, remains at a consistent width during contraction and does not get smaller (not D).
Based on this explanation, the correct answer to the provided question is: E) A, B, and C are correct.