7.92 nominal use of 'wh'-clauses

When you want to refer to matters which are not certain or definite, or about which a choice has to be made, you can use clauses beginning with a 'wh'-word or 'whether', like the clauses used for reported questions. They can be used after prepositions, and as the subject of verbs such as 'be', 'depend', and 'matter'.

• ...the question of who should be President of the Board of Trade.
• The State is desperately uncertain about what it wants artists to do.
• What you get depends on how badly you were injured.
• Whether I went twice or not doesn't matter.
• Whether you think they are any good or not is irrelevant.

7.93

Structures consisting of a 'wh'-word plus a 'to'-infinitive clause, which refer to a possible course of action, are used after prepositions but not usually as subjects.

• ...the problem of what to tell the adopted child.
• ...a book on how to avoid having a heart attack.
• People are very worried about how to fill their increased leisure time.