Answer:
The correct answer will be option A - A-band.
Step-by-step explanation:
The sarcomere is the repeating unit of a myofibril which extends between two z-lines. Under a microscope, a sarcomere can be divided into A- band which is composed of thick myosin only and I-band which consists of thin filament that is actin only.
When a muscle contract then actin and myosin comes in overlapping position due to which I-band shortens and between two z-lines and overlapped structure of thin actin filaments over thick myosin filaments (A-band) is seen.
Therefore, only A-band is seen between two z-lines in a contracted muscle thus, option A is the correct answer.