pls helpppp!!! Due todayy I will give brainliest I will give 30 points :)

(Ukulele)

1) What note is the "root" of the C chord? ___


2) What note is the "root" of the B chord? ___


3) Write the note names of the following chords...
C chord
F chord
C7 Chord


4) Why are 7th chords called "7th Chords"? ___