I'm learning grammar... there's possible that someone help me saying if these sentences are correct? Affirmative Statement: Andrew must sometimes have picked up to Susan. Negative Statement: Andrew must not sometimes have picked up to Susan. Yes/ No questions: Must Andrew sometimes have picked up to Susan.? Yes, he must. No, he must not. Wh-questions: When must Andrew sometimes have picked up to Susan? Andrew must sometimes have picked up to Susan on Sundays. Could you tell me please if these sentences are correct? I'm trying to use past modals in different sentences with adverbs of frequency