The manager raised his voice ---------- he could be heard cl

选B,为了让别人听得清楚,经理提高了他的声音。A、C选项 in order to/so as to do sth,正确的句子应该是：The manager raised his voice in order to/so as to be heard clearly。不选D选项,因为句子里面不能出现两个谓语动词,make sure不能直接跟在后面,正确的句子应该是：The manager raised his voice to make sure he could be heard clearly。