![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
Based on the research, Niswander cautions that
A.
the practice of recommending folic acid for the pregnant needs reconsidering.
B.
it is still controversial whether folic acid is good for human fetuses.
C.
it is too early to judge the effects of folic acid.
D.
pregnant mothers cannot take an overdose of folic acid.