{guitar}
when you change between the c and d7 chords, you would use

a common finger
a guide finger
both a common finger and a guide finger
no common or guide fingers

when you change between the g and c chords, you would use

a common finger
a guide finger
both a common finger and a guide finger
no common fingers or guide fingers

read the following passage:

you will improve with practice. if your left hand starts to hurt or feel uncomfortable, you may practice the chords without pressing the strings down. this is a painless way to get used to new chords.

based on what you've read, which of the following could you infer?