only by shouting at the top of his voice ______
a)was he able to make himself heard
b)he was able to make himself heard
c)was he able to make himself hear
d)he was able to make himself hear
[答案 a ]
请帮我解释一下

基本同意楼上意见.
PS:
这个句子当中有两个考点:
第一,only位于句首,后跟状语时需要倒装.
第二,make的知识点:make + oneself + done 表示“使自己被……”或“让别人……”
make在这里是“使”，“让”的意思，done代表动词的过去分词，在这里作宾语补足语，含被动意义。