Fill in the blanks with appropriate modals:

He…………………. finish this work before I go.

must

The modal must is the most appropriate modal to fill in the blank. The modal must is used to express certainty or strong obligation. In this case, the speaker is stating that the person must finish the work before the speaker goes because it is important that the work is done.

The other options are incorrect.

• Has to is also used to express obligation, but it is not as forceful as must.
• Should is used to express advice or a suggestion, but it is not used to express certainty or strong obligation.
• Will is used to express certainty about something that will happen in the future, but it is not used to express certainty or strong obligation.