A memoir can be based upon a person or even an event. They are most commonly used after a person has passed or went away somewhere. They are used to help keep memories and celebrate the person. Some must haves can include photos,words,or even things they enjoyed.
When migrating, birds usually migrate when there's not enough food, shorting of daylight, and when it's getting colder in winter. Birds that migrate do so in the late summer through the fall and in the late winter through the spring. Birds and use a radical pair-based compass to "see" the Earth's magnetic field when migrating.
I think maybe C? Not sure though, so don't take my word as gospel :)
