What is the phase that the fusion in a star no longer occurs

Providing immunity by injecting the body with a weakened form a pathogen is known as

If bacteria are much too small to see, what is one reason why can we see colonies in the petri dishes that have plenty of food to eat after only a few days?

In the diagram below, the northern hemisphere would be in what season at position a a.fall b. winter c.summer d.spring