Hi, As I am reading Oxford PracticeGrammar, found this in the index pages:
1. with to infinitive form.
We'll have to decide whether to go( to infinitive) ahead with the project. One can't use the 'if' form.
The same with: I was wondering whether to order(to infinitive) some coffee or tea.
2. Direct question:
'Has the taxi arrived jet?' 'No, not jet'
Reported question - indirect question:
Someone was wondering if/whether the taxi (noun) has arrived yet.
'Can we take photos?' -'Yes, of course.' ---> The visitors wanted to know if/whether they (noun) can take photos.