Final answer:
The world's oldest monotheistic religion, Judaism, originated in modern-day Iraq. Abraham, a key figure in the religion, came from Mesopotamia according to the Hebrew Bible.
Step-by-step explanation:
The world's oldest monotheistic religion, which believes in the worship of one God, is Judaism. This ancient faith traces its origins back to the Hebrew prophet Abraham. According to the Hebrew Bible, Abraham originally came from Mesopotamia, which corresponds to modern-day Iraq. Thus, the correct answer to the question 'The world's oldest monotheistic religion originated in which modern-day country?' is b) Iraq.
It is important to note that while Hinduism is the oldest religion, it is not monotheistic. Hinduism, with its belief in multiple manifestations of the divine, originated around 4500 years ago in what is now modern-day northwest India and Pakistan. On the other hand, the monotheistic tradition of Judaism began with Abraham and was later solidified through the laws given to Moses, who emphasized the worship of only one God, Yahweh.