基准试剂主要成分含量一般在()。
A、99%~100%
B、99.9%~101%
C、99.990%~99.95%
D、99.95%~100.05%
参考答案:D
方程x2-2x=0的解是( )。
____ has been proved again and again that ____ is said in the ads greatly affects people’s impression of the products.
A.There; what
B.There; that
C.It; which
D.It; what