目前效果肯定、易于推广应用的防龋方法是
A．中药牙膏刷牙
B．酶防龋
C．防龋涂料防龋
D．氟化物防龋
E．糖代用品防龋
参考答案：D
粮豆在农田生长期和收割时混杂的有毒植物种子有（）。
A.麦角
B.毒麦
C.菜籽
D.麦仙翁籽
E.苍耳子
Gender imbalance has become a serious problem in China, _______ the Chinese government is giving serious thought to.
A．the one
B．that
C．one
D．those
