对体内脂类代谢特别是胆固醇代谢十分重要的是（）
A.必需脂肪酸
B.膳食纤维
C.无机盐
D.维生素
参考答案：A
________ the opportunity to speak at the graduation ceremony made him overjoyed.
A．Being offered
B．To offer
C．Having offered
D．Offered
高级孔板阀清洗怎样操作。
