I didn't know that there had been an accident

When we are discussing alternatives or expressing doubt, we can use whether should or whether to after most of the above verbs: / haven't decided whether I should go/whether to go to Spain We can sometimes use if as an alternative to whether before a clause, but not before an infinitive [compare > 15.18n.5, 15.24.2].

Remember and forget can be followed directly by a to-infinitive: / remembered to/forgot to switch off the lights [>16. 59]

Learn can be followed by to or how to without any change in meaning

when it refers to acquiring a skill:

/ learnt to/how to ride a bicycle when I was four

However, learn must be followed only by to (Not "how to*) when it

conveys the idea of learning from experience:

We soon learnt to do as we were told in Mr Spinks' class '

16 The infinitive and the '-ing form

16.25 Verb + object + question-word + to-infinitive or a clause

Advise, instruct remind, teach and tell can have an object +

- a to-infinitive [> 15.24.1]: He told us to run My sister taught me to swim

- any question word (except why) + to-infinitive: The receptionist told me where to wait

- a clause [> 15.24.2]:

The union leader told the men that they should go back to work The union leader told the men when they should go back to work Persuade and warn can have toor that but not a question-word: He warned me to stay away He warned me (that) I was in danger

The verb show can be used like the verbs above, except that it always requires a question-word before the to-infinitive: Please show me how to start the engine

Object + whether + to-infinitive can be used after: advise/not advise ask/not ask show/not show not teach, not tell and in questions with these verbs:

Can you advise me whether to register this letter?

You haven't told me whether to sign this form

Adjective + to-infinitive