硝酸盐还原试验如果不显红色时,应加入的试剂是
A.肌酸苷
B.肌酸
C.锌粉
D.硫磺粉
E.铜粉
参考答案:C
下列图中动物的行为属于学习行为的是:
A.①②④
B.①③④
C.①②③
D.②③④
The employment rate has continued to rise in big cities thanks to the efforts of the local govenments to increase .
A.then
B.those
C.it
D.that