Read the excerpt from "return flight."

the crate was used to move him back and forth between the myriad enclosures that made up his strange life on the ground. these creatures seemed to like their enclosures. they spent most of their time inside one kind or another. he didn't understand it. if he hadn't found himself at the mercy of these cage lovers, he would be soaring in the wide open space of the sky, forever free of any kind of container.

according to the excerpt, the crate is most likely a symbol of

civilization.
wilderness.
injury.
love.

civilization

Explanation: the crate takes him from the wild and into civilization

The crate is indeed a symbol of civilization.

Explanation:

From this excerpt, we can understand the narrator is probably a bird. His "life on the ground" always seems to revolve around crates. He is never free, constantly being transported inside a cage of some sort. That is beyond his comprehension, since he'd much rather be flying freely. But he assumes humans have a need, even a love, for cages. "They spent most of their time inside one kind or another." Houses and cars, which are a part of civilization, may be seen as a crate to a wild animal. To him, thus, crates represent civilization, and civilization apparently represents some sort of prison.

i guess you are missing the idea that has to be supported, am i right?