A:should be; be operated on
B:were; must be operated on
C:be; was operated on
D:was; be operated on
都含有能消化糖类、蛋白质和脂肪的酶的一组消化液是( )
我国婚姻法规定:禁止近亲结婚,其原因是( )
我国两个特别行政区分布在( )
关于生态系统中各成分功能的阐述,正确的是( )