If, that,

[Silverobama]

Hi,

I don't doubt ___ he took the first place in his class, but I do doubt ___ he will succeed in the end.

a)If; that
b)but; which
c)whether; whether
d)that; whether

I guess the answer is A, am I right? But I don't know why, can anyone help?

[5jj]

There is almost always an idea of uncertainty when we use if. With some verbs expressing in themselves lack of certainty it appears that that andif can both be used, with little practical difference in meaning between:

1. I doubt if he was there.
2. I doubt that he was there.

In #1 the uncertainty about his being there may be stronger than in #2; only the context of the utterance can make this clear. The difference is not important for practical purposes.

With absence of doubt we return to certainty, and that is now the only appropriate choice:

3. I don't doubt that he succeeded.

[Silverobama]

Thanks a lot, so the answer of this question is a?

I got this question from my student's practice book.

[Raymott]

Thanks a lot, so the answer of this question is a?

I got this question from my student's practice book.

I'd choose c.

[5jj]

I'd choose d, assuming that 'chat' should read 'that'.

[Silverobama]

Sorry, it should have been "that", it was a typo. I've corrected it.

Thanks a lot

But I still don't understand why you choose d rather than a.

[Raymott]

Yes, d would also work, now that it's fixed. a and c are also possible.
Given that there are stylistic choices which differ among dialects, the only wrong answer is b.

[emsr2d2]

I'm with 5jj. If you doubt something, then there are some alternative outcomes and you are not sure which one will happen (or has happened) therefore "whether" is fine. However, stating "I don't doubt ..." means that you already know the fact, the outcome etc so "whether" and "if" are not appropriate. For me "I don't doubt" means much the same as "I know for a fact" or "I completely believe", and can therefore only be followed by that.

I doubt whether [or not] he can jump over that wall.
I don't doubt that he can jump over that wall.

I doubt whether [or not] Obama is up to the task.
I don't doubt that Obama is up to the task.

He doubts whether [or not] the planet will still be here in 5 million years.
He doesn't doubt that the planet will still be here in 5 million years.

[Raymott]

For me "I don't doubt" means much the same as "I know for a fact" or "I completely believe", and can therefore only be followed by that.

So, is the following wrong in BrE then, ems? It sounds alright to me.
"I know for a fact whether he can jump over the wall [or not]. He can."

[emsr2d2]

So, is the following wrong in BrE then, ems? It sounds alright to me.
"I know for a fact whether he can jump over the wall [or not]. He can."

That sounds unnatural to me. I can see how an argument can be made for it, but I would see it as an unnecessary and very roundabout way of saying "I know for a fact that he can jump over the wall". Having said that, I find "I know for a fact whether ..." more natural (or rather, less unnatural) than "I don't doubt whether ..."

I'm really not sure I can put my finger on what I find so unnatural about it. I considered a few alternatives and realised that I find "I have no doubt at all as to whether he can jump over that wall or not" fairly satisfactory, but not "I don't doubt whether ...".