The grammar presented is based on the grammar of written and spoken English as it is used in college lectures, textbooks, academic essays, high school classrooms, and coversations between instructors ...

The present perfect is often used to say whether an action has happened or not at the present time. The action might be necessary or expected by someone, and we want to say if it is complete or not.

In English, we can express sentences in two different ways: active voice and passive voice. The active voice is used when the focus is on the subject (or agent) of the main verb. This is the ...