The correct answer is D.
The mother is jeering at her son, which means she is mocking or ridiculing him. She is asking him whether he supposes that he knows better than his father. This suggests that she believes that her son is being arrogant and disrespectful by thinking that he knows more than his father.
Option A is incorrect because the mother is not asking if her son is supposed to know better than his father. She is asking if he supposes that he knows better.
Option B is incorrect because the mother is not asking whether her son knows better than his father. She is asking if he supposes that he knows better.
Option C is incorrect because the mother is not asking whether her son supposed that he would know better than his father. She is asking if he supposes that he knows better.