Question

Sincere people abide............their promise.
a.by
b.of
c.at.
d.on​

Answer 1

Sincere people abide of their home.

Answer 2

Sincere people abide by their promise.

Answer: Option a.

Explanation:

'By' is a preposition. 'By' as a preposition is used to show that a person or thing does something.

Prepositions are the words that connect between a 'noun or pronoun' and some other word in a sentence for the completion of the sentence.

Examples of preposition are by, up, at, over, far from, in accordance with instead of, ahead of.

Preposition indicates place, time, direction and prepositional phrase.  

Preposition help in framing and understanding the sentence better.

• Prepositions are always in prepositional phrases - at home, during the stay, over the cave.