If and if

If and if guide predicative clauses

What is generally used when guiding predicative clauses. For example:

The question is where they can cooperate with us. The question is whether they can cooperate with us.

The question is whether we can get there in time.

Some grammars think that if can also guide predicative clauses, such as:

The first question I asked him was whether he would do it.

Our only problem is that if someone comes up with this good idea first.

But for middle school students, it is better to avoid this usage from time to time.

Help wholeheartedly, hope to adopt! ! ! !