换热器的效能（有效度）
参考答案：
换热器的实际传热量与最大可能传热量之比。
_____ I know the money is safe, I shall not worry about it. [ ]
A. Even though
B. Unless
C. As long as
D. While
贝类的主要呈味物质为琥珀酸及其钠盐。( )
