统一规定测定产量因素的作物有（）。
A.水稻、小麦
B.玉米、棉花
C.大豆、油菜
D.高粱、胡麻
参考答案：A, B, C
扩孔镶套法
This box is too heavy for me to carry it upstairs.（）
A.You may ask for help.
B.I'll give you a hand.
C.Please do me a favor.
D.I'd come to help.
