Modals: They are verbs which are used before the main verb to express ability, possibility, obligation, permission, suggestion, request, certainty or necessity.They indicate the attitude, intention and the mood of the speaker.

• They cannot be used alone in a sentence.
• In case of Questions they are used alone.
• They are not affected by the change in person i.e. first, second or third form.
• Present Participle or Past Participle form of a verb is never used with a modal.

Use of Ought to:

Ought is also a modal verb. The same form ought is used for Present and Future tenses. It is also used in Past when preceded by a verb in Past tense or followed by a Perfect infinitive, Ought is always followed by full infinitive to : e.g.

   (a) I ought to write to her today tomorrow.

In the question : -

1. You ______________ have come to the meeting. It was interesting.

In this sentence , ought to is the correct modal that can be placed in the blank part as it is used to denotes  what you advise or recommend .

2. Children ____________  be able to read by the age of 7.

In this sentence , ought to is the correct modal that can be placed in the blank part as it is used to denotes what you expect or would like to happen .

3. Nurses _________  earn more.

In this sentence , ought to is the correct modal that can be placed in the blank part as it is used to denotes what you expect or would like to happen .

Thus , the Correct Option is C , which is 1. Ought to 2. Ought to 3. Ought to .

Modals: They are verbs which are used before the main verb to express ability, possibility, obligation, permission, suggestion, request, certainty or necessity.They indicate the attitude, intention and the mood of the speaker.

• They cannot be used alone in a sentence.
• In case of Questions they are used alone.
• They are not affected by the change in person i.e. first, second or third form.
• Present Participle or Past Participle form of a verb is never used with a modal.

Use of Ought to:

Ought is also a modal verb. The same form ought is used for Present and Future tenses. It is also used in Past when preceded by a verb in Past tense or followed by a Perfect infinitive, Ought is always followed by full infinitive to : e.g.

   (a) I ought to write to her today tomorrow.

In the question : -

1. If he started out at nine, he ___________  be here by now.

In this sentence , ought to is the correct modal that can be placed in the blank part as it is used to denotes what has probably happened or is probably true .

2. That ___________  be enough food for the four of us.

In this sentence , ought to is the correct modal that can be placed in the blank part as it is used to denotes  what has probably happened or is probably true .

Thus , the Correct Option is A , which is 1. Ought to 2. Ought to .

Modals: They are verbs which are used before the main verb to express ability, possibility, obligation, permission, suggestion, request, certainty or necessity.They indicate the attitude, intention and the mood of the speaker.

• They cannot be used alone in a sentence.
• In case of Questions they are used alone.
• They are not affected by the change in person i.e. first, second or third form.
• Present Participle or Past Participle form of a verb is never used with a modal.

Use of Ought to:

Ought is also a modal verb. The same form ought is used for Present and Future tenses. It is also used in Past when preceded by a verb in Past tense or followed by a Perfect infinitive, Ought is always followed by full infinitive to : e.g.

   (a) I ought to write to her today tomorrow.

In the question : -

1. We ___________  respect our parents.

In this sentence , ought to is the correct modal that can be placed in the blank part as it is used to denotes  advice, moral obligation, duty .

2. I knew , I ___________  write to her.

In this sentence , ought to  is the correct modal that can be placed in the blank part as it is used in past when preceded by a verb in Past tense or followed by a Perfect infinitive, Ought is always followed by full infinitive to .

Thus , the Correct Option is C , which is 1. Ought to 2. Ought to .