Which of the following sentences has a 'modal verb'?

Question

Accepted Answer

Here's a detailed explanation for the given question:

**Understanding Modal Verbs:**
Modal verbs are a type of auxiliary (helping) verb that express necessity, possibility, permission, ability, obligation, or advice. They are always used with a main verb in its base form. Common modal verbs include *can, could, may, might, must, shall, should, will, would*.

**Justification for Option 4 (Correct Answer):**

*   **Option 4: "You must improve your spelling."**
    *   In this sentence, the word **'must'** is a modal verb.
    *   'Must' expresses **necessity or strong obligation**. It indicates that improving spelling is required.
    *   It is followed by the main verb 'improve' in its base form.
    *   Therefore, this sentence clearly contains a modal verb.

**Explanation for why other options are incorrect:**

*   **Option 1: "Seeing is believing."**
    *   This sentence uses 'seeing' and 'believing' as gerunds (verb forms ending in -ing that function as nouns). 'Is' is a linking verb (a form of the verb 'to be').
    *   There are no modal verbs present in this sentence.

*   **Option 2: "Her sister known to me."**
    *   This sentence is grammatically incomplete as it lacks a main verb (it should ideally be "Her sister *is* known to me" or "Her sister *was* known to me").
    *   Even if we infer a 'be' verb (like 'is' or 'was'), 'known' is a past participle acting as an adjective, and 'is'/'was' are forms of the verb 'to be', not modal verbs.
    *   There is no modal verb in the given sentence.

*   **Option 3: "She comes here to study."**
    *   In this sentence, 'comes' is the main verb, in the simple present tense.
    *   'To study' is an infinitive phrase, indicating purpose.
    *   Neither 'comes' nor 'to study' contains a modal verb.