表面式换热器与混合式比较，其传热效率（）。
A.高
B.低
C.不变
D.先高后低
参考答案：B
The earliest English ___ was written in a kind of English that is now difficult ___.
A．poem; to understand
B．poet; to be understood
C．poetry; to be understand
D．poetry; to understand
常用诊断干燥综合征的核素显像方法是（）。
A.甲状腺静态显像
B.脑脊液显像
C.唾液腺显像
D.脑血流灌注显像
E.肾动态显像
