Sitting patiently, my mother read a magazine in the waiting room. a. sitting patiently b. in the waiting room c. my mother read d. read a magazine

The participial phrase here is A, sitting patiently. Because all other answers are not correct. In the waiting room is adverbial phrase for place, my mother read is just a regular sentence, not a phrase, as well as read a magazine. So the answer is A, sitting patiently, as sitting is present participle.