If only he ________ quietly as the doctor instructed, he would not suffer so much now．
A.liesB.layC.had lainD.should lie在线课程C
解析：
这是一个对过去和现在真实情况进行假设的混合虚拟条件句。根据句子意思：如果他当初遵照医嘱卧床静养，他不至于现在受这样的苦。主句he would not suffer so much now．是对现在的事实进行虚拟假设，而从句If only he _{____} quietly as the doctor instructed是对过去事实进行虚拟假设，其结构是had done。