The child ought to be reading by now.
2.
Ought to + have + a past participle, referring to past time, indicates that
a duty has not been done or, in the negative, something wrong has been done.
E.g.: You failed; you ought to have studied more. You ought not to have wasted your time.
k. be going to
Be going to implies prior or planning, or suggest a process leading to an
action.
E.g.: Ridho is going to apply for a position in the Foreign Service.
l. Have to
Have to , like must, expresses unavoidable obligation or necessity. Have to
is interchangeable with must in affirmative sentences and is often used instead of must in negative sentence.
E.g.: We must leave by 6:00. We do not have to leave by 6:00.
We must not leave before 6:00. We are prohibited from leaving Unlike the modal auxiliaries, have to change its from to indicate time and
person. I
You have to, had to, have had to, will have to
We They
HeShe has to, had to, has had to, will have to
In addition, „have to‟ has several usage, these are: 1.
Have to is used, with a following infinitive, to express the idea of obligation. E.g.: How often do you have to travel on business?
Sorry I have to go now.
2. Have to is used to make a distinction between habitual or repeated obligation,
and non-habitual obligation. When there is the idea of repetition we use ordinary verb-forms, with do in questions and negatives.
E.g.: I dont usually have to work on Sundays. Do you often have to speak French in your job?
3. When people are talking about one thing that they are obliged to do, it is more
usual to use got-forms. E.g.: I havent got to work tomorrow.
Have you got to do any interpreting this week? 4.
Got-forms are unusual in the past, and are replaced by ordinary verb-forms of infinitive and participles.
E.g.: Did you have to go to Church on Sundays when you were a child?
5. To talk about the future, both have to and will have to are common.
E.g.: Ive got to get up early tomorrow. Were going to Devon.
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m. Used to
Used to expresses the idea of a customary or habitual action in the past.
E.g.: it used to take weeks to cross the ocean by ship.
n. be to
Be to is used to indicate plans and arrangements.
E.g.: I am to telephone him tomorrow at 5:00.
It has been arranged that I will telephone him tomorrow.
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o. Need
Need is used to express immediate necessity in the future.
E.g.: you
needn’t pay for the bill.
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http:ismailmidi.comberita-168-must-vs-have-to.html
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George E. Wishon, Julia m. Burks, Let’s write English revised edition, … p. 234.
