Conditionals.

Think carefully about what a conditional is.

mookbark

B probably

However in the rare case A is right if it's uncertain whether Fred had won anything. But in the case we'd prefer "…if he had won…"

Since the topic (chosen by the thread starter) is 'conditionals' I think we can exclude "didn't". The only other choice is "wouldn't".

Ill take your word for it Con, I'm no grammarian

The title "Conditionals" is the clue to where the question is coming from. The topic is the 'Present Unreal Conditional' - which is used to talk about what you would generally do in imaginary situations. It takes the form if ... Simple Past ..., ... would [not] + verb or ... would [not]+ verb ... if ... Simple Past ...

Fred said that if he won a lot of money he wouldn't know what to do with it.

If I owned a car, I would drive to work.

If I moved to Spain, I would live in Málaga.

Jack said he would read more if he didn't watch so much TV.

She would travel around the world if she had more money.

Anyone who has paid attention in the class about conditionals would see that "wouldn't" choice and immediately know which of the two choices is the right answer.

"Anyone who has paid attention in the class about conditionals", especially an anyone who purports to be a teacher, would know that the above is so overly simplistic as to be useless for students.

Relating to an assertion about Fred in sometime past.
"If Fred won a lot of money, he didn't know what to do with it." Sounds understandable.
Narrow possibilities, though

geez b

sorry the reason I wrote geez is because I wrote b and it wouldn't post

You just learned something about post length.

No I knew it already. I thought it would be changed by now. I still get the wait you might be a bot blah blah.....

I get it but sometimes it is annoying.

You don't look at all bottish

Maybe, at at stretch, but it's not going to be the right answer in a 2-choice test about "conditionals" that some kid in India or somewhere is doing.

You can suggest this yet you leap to this gigantic assumption, "Think carefully about what a conditional is".

That's a teacher?

The correct answer is B, because Fred has not yet won the money so the thought is a fantasy regarding future events.

Con thanks for the cari and I'm sure you're right. However after an ed including BS in Journ and a lifetime in that field, at no time had the conditional been explained