单选题 The baby is always ______ his sister by pulling her hair.
【正确答案】 C
【答案解析】解析：annoy vt．使恼火，使烦恼；打扰。enrage vt．使暴怒，使极为生气。upset vt．使心烦意乱，使苦恼，使不适；打翻，弄翻。frustrate vt．挫败，使受挫折；使灰心，使恼怒而又不知所措。