none of them

[azz]

a. The members of this party claim to know this subject well, but when you ask them a question, every one of them has nothing to say.

b. The members of this party all claim to know this subject well, but when you ask them a question, all of them have nothing to say.

c. The members of this party claim to know this subject well, but when you ask them a question, every one of them doesn't have anything to say.

d. The members of this party all claim to know this subject well, but when you ask them a question, all of them don't have anything to say.

Are the above sentences grammatically correct?

I don't think they are good sentences. I'd use 'none of them has anything to say'; but I think (c) and (d) might be used informally.

Many thanks.

[Alan]

I would say rather that (a) and (b) would pass muster conversationally, but the only fully correct standard form would be:

...none of them has/have anything to say.