Feather is a concrete nouns?

No

Explanation:

Concrete nouns are words that we often use on a daily basis, so I would say that feather is not one.

Yes.

Explanation:

"A concrete noun is a noun that can be identified through one of the five senses (taste, touch, sight, hearing, or smell). Consider the examples below: Would someone please answer the phone ? In the sentence above, the noun phone is a concrete noun: you can touch it, see it, hear it, and maybe even smell it or taste it." if you can touch, see, and taste a feather (idk why you would taste it but its possible), wouldnt it be considered a concrete noun?

the rebels’ chances of victory at lexington & concord were fairly slim, given the fact that most of them very untrained and they were up against the world's greatest military force.  

i would say b. research typically uses a variety of sources