A:3﹣甲基﹣1﹣丁炔
B:3﹣甲基﹣1﹣丁烯
C:2﹣甲基﹣1﹣丁炔
D:2﹣甲基﹣1﹣丁烯
The Monkey King can make the stick so_______that he can put it into his ear.