Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

Declaratives with must

413b

Must

occurs in commands and instructions in declarative clauses:

[teacher (A) to class]

A: 

You must be clear of what the right answer is

. Because you’re gonna mark

some of these answers. 

B: Do we write the answers in the book sir?

A: Yeah you can put your answer in the book.

Û

539 Glossary for any unfamiliar terms

Speech acts | 685

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[instructions to sales personnel at a training session]

This part of the selling process is directed towards finding out about your client

and completing the client questionnaire. With all clients 

you must attempt to

complete all relevant areas of the questionnaire

. This includes gathering hard

facts, date of birth, marital status, dependants, hobbies and so on.

[university tutor to student, discussing how long she will have to study to get

her PhD]

I think 

you must aim for three years

.

(note the softener I think)

✪

Must

in directives is very strong in English, and should be used with care,

especially in contexts such as suggesting and advising. It is normally only used

in directives by people in positions of power and authority, and even then may

be softened (e.g. the university tutor’s use of I think in the example above).