哪项符合中度高渗性脱水（）

A.失水量占体重5%，血清钠135mmol／L

B.失水量占体重6%，血清钠155mmol／L

C.失水量占体重11%，血清钠140mmol／L

D.失水量占体重7%，血清钠128mmol／L

E.失水量占体重8%，血清钠148mmol／L

When asked to explain ________ made his lessons so exciting, the teacher kept silent.

A．what it was that

B．that what it was

C．what was it that

D．that what was it