Choose the correct options. Sometimes more than one option is possible
Modals General Information
Modal verbs are special verbs that function not in a usual way in English. They give additional information about the function of the main verb that follows it. They have a great variety of communicative functions.

In most cases, modals cannot be changed. I can swim. He can swim.

Not all modals can function in the past but they have special forms to do this.

e.g. You must do it — present/future meaning. You must have done it — past meaning.

There are verbs that have the same meaning as modal verbs but they function as usual verbs. So they can be used in the past and future.

e.g. I must go now. (Present). I had to leave. (Past). I will have to go there. (Future).

Modal verbs can refer to

• present;
• past;
• future;
• all stated above.

If followed by a bare infinitive, modal verbs refer to

• a completed action or state;
• an uncompleted action or state.

If followed by a perfect infinitive, modal verbs refer to

• a completed action or state;
• an uncompleted action or state.

Choose a true sentence.

• All modal verbs don't take any endings.
• Some modal verbs need endings.

In interrogative sentences

• all modal verbs come before the subject;
• some modal verbs need auxiliary verbs.

In negations

• most modal verbs are followed by not;
• not is added to the auxiliary verb in some cases;
• not goes before the subject.