Education about sex is very important.

What does this line mean?

He is known as a person with learning.

He is an expert in ethology, and his research is highly regarded worldwide.

He is an expert in paleozoology and has a deep knowledge about the ecology of dinosaurs.

Cats are digitigrade animals, they walk on their toes.

His research mainly focuses on the plantigradism of mammals.

I saw many animals at the zoo.

The use of mobile phones is prohibited during class.

There is a class observation at my son's school tomorrow.