--instructions--

This task doesn't have audio. Read the question below and select the correct answer.

--questions--

--text--

Which sentence is grammatically correct?

--answers--

You must to complete the security training.

--feedback--

Must is a modal verb and does not use to before the base verb.

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You must completed the security training.

--feedback--

The verb after must should be in its base form (complete), not the past tense (completed).

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You must complete the security training.

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You must completing the security training.

--feedback--

Must is followed by the base verb, not the -ing form.

--video-solution--

3

--explanation--

Must is a modal verb, so it follows these rules:

• It is always followed by the base form of the verb (without to).

• It does not take -s in the third person singular.

• It does not use do/does in questions or negatives.