Question on explanation for 'seldom, rarely, and never.'

[learning54]

Hi teachers,
If you agree with the explanation, which option is better?

a) Even though the adverbs, seldom,rarely, and never, are used only withan affirmative sentence, they can express a positive or a negative idea.

b) Even though the adverbs, seldom,rarely, and never, are used only in an affirmative sentence, they can express a positive or a negative idea.

Thanks in advance​

 

[Rover_KE]

I would use in​.

 

[learning54]

Hi Rover,
Thank you for your reply. So you agree with the explanation then.
I guess this one is even better:
Even though the adverbs, seldom, rarely, and never, are used only in affirmative sentences, they can express a positive or negative idea.