1. Birds learn to fly By instinct.
   鸟学飞出自本能。
2. Fifty planes will fly by the castle as a mark of respect.
   50架飞机将飞过城堡以示敬意。
3. Birds fly by instinct.
   鸟生来会飞。
4. Birds learn to fly by instinct.
   鸟儿学飞是出于本能。
5. Airplane pilots must always fly by the book.
   飞行员应按规则飞行。

　2个动词解释