E.g.: Must I clean all the rooms? Why must you always leave your dirty clothes in the bathroom?
59
-
Function of Must in deduction
1. Must can be used to say that we are sure about something because it is
logically necessary. E.g.: Mary must have some problem: she keeps crying.
Im in love. That must be nice. Theres the doorbell. It must be Roger.
2. Must is only used in this way in affirmative sentences. In questions and
negatives we use can or cant instead. E.g.: That cant be the postman. Its only seven oclock.
What do you think this letter can mean? 3.
Must is used with the perfect infinitive for deductions about the past. can and cant for questions and negatives
E.g.: We went to Majorca. That must have been nice. The lights have gone out. A fuse must have blown.
I dont think he can have heard you. Call again. Where can John have put the matches?
He cant have thrown them away. 4.
In reported speech, must can be used after a past reporting verb as if it were a past tense. Only in that case, must refers to the past.
E.g.: I decided that I must stop smoking. I felt there must be something wrong.
60
j. Ought to
1.
Ought to, like should, express desirability, avoidable obligation, or duty. It relates to present or future time. Ought to and should are often used
interchangeably.
E.g.: You ought to study more. If you want to learn
59
http:ismailmidi.comberita-168-must-vs-have-to.html
60
http:ismailmidi.comberita-168-must-vs-have-to.html
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.
