The israelite religion focused on only one god which is called: *
a. polytheism
b. christianity
c. monotheism
d. hinduism

it's definitely not A (this means religion with Many gods) and not D (It's an Indian religion with many gods)

now, C Monotheism just means belief in one god: it's a good answer, but Monotheism includes many religions, for example Islam.

B. is technically right, as Christianity is both monotheistic and started by Israelites (the descendants of Jakob). But this is not the way you would usually describe Christianity.

The best answer would be Judaism, but it't not an option.

So, i think that you can argue for Christianity, since it split out of Judaism, but the question suggests Judaism rather than Christianity... it's just very unfortunately phrased.