Final answer:
Abraham was 100 years old and Sarah was 90 years old when their son Isaac was born, according to the book of Genesis in the Hebrew Bible.
Step-by-step explanation:
The ages of Abraham and Sarah when Isaac was born are detailed in the Hebrew Bible, specifically in the book of Genesis. According to Genesis 21:5, Abraham was 100 years old when his son Isaac was born. The book of Genesis also mentions that Sarah, Abraham's wife, was 90 years old when she gave birth to Isaac (Genesis 17:17).
Therefore, the correct answer to the question 'How old were Abraham and Sarah when Isaac was born?' is B) Abraham: 100, Sarah: 90. This event is a fundamental story within the
Abrahamic religions and has significance in religious history and theology.