参考答案

正确答案：D
解析：在含有主语从句的复合句中，如果主句的谓语是由某些动词的被动式构成的，则必须把形式主语it置于句首，而将实际主语(即主语从句)置于句尾。常见的这种句型有：It is suggested that…, It is believed that…, It is said that…, It is recorded that…, It must be pointed out that…, It has been proved that…等。