Class 11 NEET Biology Locomotion and Movement

The correct option is (1) because the length of A-band is retained. During muscle contraction, the following events occur:
(1) The globular head of myosin acts as ATPase and hydrolyses ATP molecule and eventually leads to the formation of cross bridge.
(2) This pulls the actin filament towards the centre of 'A-band'.
(3) The Z-line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere.
(4) The thin myofilaments move past the thick myofilaments due to which the H-zone narrows.
This reduces the length of I-band but retains the length of A-band.
(5) The myosin then releases ADP+Pi, and goes back to its relaxed state.