题干
He wants to make his invention more successful, so he it for many times.
A：designed
B： redesigns
C：plan
D：plans
答案(点此获取答案解析）
B
He wants to make his invention more successful, so he it for many times.
A：designed
B： redesigns
C：plan
D：plans
，
在
上的投影为
，
轴上的投影为2，且
，则