是class starts 还是class begin

是class starts 还是class begin 是class is begin还是class begin 是用Class begin 还是Class begins 是Class begin.还是Class begins.还是Classes begin.为什么? 是before class begin 还是before class is begin "class begin"还是"classes begin"? Begin the class at the class还是in the class还有是in class还是at class.晕了. Let's begin our class. when dose the class begin? It''s time to starts our class. 是of our class,还是for our class?