-- himself -- clearly ,he raised his voice.A.So as to make;heared B.In order to make;hear

选 C
To make himself heard clearly,he raised his voice.
为了能让大家清楚地听到他讲话,他提高了嗓音
make oneself heard 使某人自己说话被听到,就是让别人都能听到自己说话
make 后有三种形式 ：
make sb.adj.让某人adj.有时会见到
make sb.done也属于这种形式,使某人怎样,让某人怎样.比如make you surprised让你吃惊
make sb.n.让某人做n.比如make you monitor让你做班长
还有就是make sb.do sth
in order to可以用在句首或句末,
但so as to只能用在句末,所以A也是错误的