I wonder _______next month.
A:where they have the boat races
B:whether they will have the boat races
C:they will have the boat races
D:whether they have the boat races
名著阅读实践活动。
直角△ABC中,∠BAC =90°,D、E、F分别为AB、BC、AC的中点,已知DF=3,则AE= ____ .