Please help with the questions

What protects the lining of the stomach from acidic gastric juices?

The diagram shows a fossil of an ancient whale skull and a skull of a present-day whale. the ancient whale is extinct and is believed to be an ancestor of the present-day whale. what do these skulls most likely show that supports darwin’s theory of evolution? all populations can adapt and survive. only some organisms have a common ancestor. populations change slowly over time. populations rapidly become extinct.

The mixture of sperm and fluids from the seminal vesicles, prostate gland, and cowper's glands is called