在体内合成胆固醇的原料是
A．丙酮酸B．草酸C．乙酰CoAD．α-酮戊二酸E．苹果酸
参考答案：C
No sooner had we reached the top of the mountain ______ we all sat down to rest.
A. when B. thenC. than D. until
什么是锅炉受热面变形事故？
