我国生产的淀粉品种主要有（）、（）、（）
参考答案：玉米淀粉；木薯淀粉；马铃薯淀粉
The time and effort he has devoted during the past few years _____ trees in that village are now considered to be very important.
A．to planting
B．to plant
C．plant
D．planting
利用电场效应来控制电流的PN结称为场效应管。
