Which religion teaches that God promised to bless Abraham's descendants if they worshiped the one true God

a. IslamB. JudaismC. ChristianityD. Sufism

The best answer is Judaism and it's one of the most important part of Judaism.

However, to some extent options a) and c) are also correct: they are, together with Judaism, called Abrahamic religionsand they all believe that God directed and protected Abraham.