During fertilization in amphibians, the fusion of egg and sperm plasma is preceded by
(P) Release of enzymatic contents from the acrosomal vesicle through exocytosis.
(Q) Binding and interaction of the sperm to vitelline membrane
(R) Chemo-attraction of the sperm to the egg by soluble factors secreted by egg.
(S) Release of the sperm nucleus into the ooplasm.
Which of the following is the correct sequence?

The correct option is A R-Q-P-S
Fertilisation in amphibians takes place by following steps-

1. Release of sperms in the water.
2. Chemo-attraction of the sperm to the egg by soluble factors secreted by egg.
3. Binding and interaction of the sperm of vitelline membrane.
4. Release of enzymatic contents from the acrosomal vesicle through exocytosis.
5. Release of the sperm nucleus into the ooplasm.

So, the correct option is 'R-Q-P-S'.