Present Simple is used for habits, routines.

Dara .......... at 5 o'clock every morning.

Subj. + to be + V_ing + Obj.

..........................is used for action which is happening now.

Vichea and Dara ...............their exam right now.

Subj. + have/has + V₃ + Obj.

Present Perfect is used to talk about the action which happened in the past and continue to the present.

Maly .......... in Udong High School for 5 years.

...................is used to talk about the action which already happened in the past

In 2019, students ................. online with teachers at their houses.

Subj. + was/were + V_ing + Obj.

................................is used to talk the action which was happening with a specified time in the past.

Saly ................... a novel when his mother cleaned his room.

While the teacher ........... my class, Mr.Sok came to the classroom.

Subj. + had + V₃ + (obj.)

........................is used to talk about the past action which happened before another action in the past

Lyly ........... her homework before her teacher came to the class.

Subj. + will + V_b.f + Obj.

......... is used to make immediate decision and express promise, request.

Mr. Seng ................ you a book tomorrow.