为什么孕期妇女要补充叶酸？（）
A.有效地预防胎儿神经管畸形
B.有效地预防小儿麻痹
C.有助于胎儿脑部发育
D.有效预防早产
参考答案：A
What does the speaker imply
A．Your food is special.
B．Your food is nice.
C．You are picky about food.
D．You like some particular food.
根据《建筑工程冬期施工规程》-JGJT104-2011规定，当设计无要求，且最低气温等于或低于（）时，砌体砂浆强度等级应较常温施工提高一级。
A.5℃
B.0℃
C.10℃
D.15℃
