What helps in the penetration of egg by the sperm

Vas deferens receives a duct from seminal vesicle and opens into urethra as _________.

The rule of embryonic development was given by

After gastrulation the roof of archenteron is formed by

In the embryonic development of chordate the animal pole forms one of the following of the adult

Which one of the following is the effect of higher $pH$ on the sperms