During the muscle contraction, which zone decreases?
a)	I-zone	b)	Z-zone	c)	H-zone	d)	M-zone

(c)

According to sliding filament theory, when a fibril contracts its ‘A’ bands remain intact, while the ‘I’ bands progressively shorten and eventually disappear. At this stage, ‘H’ zones also disappear because the active filaments of both the sides in each sarcomere may even overlap each other that the ‘M’ line and ‘Z’ lines and touch the ends of myosin filaments.