The correct answer is '(a)'. Key Points - The error lies in Part (a) of the sentence. - The meaning of the phrasal verb 'point at' is to show the position or direction of something by extending a finger or other pointed object towards it. - Example: The librarian pointed at the sign that said to keep quiet. - Therefore, the use of 'over' in Part (a) of the sentence should be replaced with 'at' to make it grammatically correct. - Therefore, the correct answer is '(a)'. Correct sentence: He began his discussion by pointing at that men and women had different biological functions.
