下列食品制作应用发酵技术的是（ ）
A：米酒
B：豆芽
C：鲜奶
D：地瓜干
对于平抛运动，下列说法正确的是（ ）
设α为平面，a、b为两条不同的直线，则下列叙述正确的是（ ）
His family are worried about him because they haven't __________ letters from him for a long time.
