We should abide (1)/ to the promise (2)/ that we make. (3)/ No error (4)

Answer

2

Explanation

by will replace to because
abide (Verb) agrees with by (Prep.)
abide by something (Phr. V.) : to accept and act according to a law, an agreement, etc.
Look at the examples given below:
You.ll have to abide by the rules of the club.
We will abide by their decision
Hence, by the promise Is the right usage .