Statement A:  In majority of algae and fishes fertilization is external.
Statement B: External fertilization shows great synchrony between the sexes.

detailed solution

Correct option is C

In most aquatic organisms, such as a majority of algae and fishes as well as amphibians, syngamy occurs in the external medium (water), i.e., outside the body of the organism. This type of gametic fusion is called external fertilisation. Organisms exhibiting external fertilisation show great synchrony between the sexes and release a large number of gametes into the surrounding medium (water) in order to enhance the chances of syngamy.