"with ears forward/with eyes watchful" AND "in whose limbs there is latent flight"
The poem compares people to deer. In Option III it's describing how a deer's legs are always ready to run off because they are cautious. Option II also shows the deer being on alert for possible dangers with his ears forward and eyes on the lookout. Option I does not show the alertness. Instead it shows pride and determination.
You could write a poem talking about the benefits and detriments of eating those foods or you could write one about how long it would take for those foods to expire.