They will not decide their attitude until they______what the speaker has to say.
【正确答案】 A
【答案解析】解析：这是一道语法题，考点是动词时态。“听到说话人要讲的内容”要发生在“决定自己的态度”之前，因此要用完成时have heard。因此A为正确答案。