Could anyone solve these questions with explanations?

Could anyone solve these questions with explanations?

You can eliminate a and c because they are the same ideas, so and. d
Another way would be to look at the sentence and focus on the word “ironically”. The party leaders are building a “progressive party”, so progressive legislatures should have supported them, but ironically they must have not. So d again
Thank you, but I still don’t get 5.
“The party leaders encountered no greater obstacle to their efforts” how is this a irony?
It is ironical because their (the progressive party’s) biggest obstacle were progressive legislatures
no greater obstacle than “x” means “x” was the biggest obstacle