Final answer:
The temple of Karnak in Egypt was begun around ca. 1550 BCE during the start of the New Kingdom era, making option 1 the correct answer.
Step-by-step explanation:
The Beginning of Karnak, Egypt
The temple of Karnak, located in ancient Thebes, began its initial development during the Middle Kingdom of Egypt which spanned from 2055 to 1650 BCE. However, the most extensive work on Karnak occurred during a later period. Based on historical timelines and the information provided, the beginning of the temple's major construction phase aligns with the start of the New Kingdom, which is ca. 1550 BCE.
This would make option 1) ca. 1550 BCE the correct answer for when Karnak was begun. It's important to note that while Karnak was added to by various pharaohs, leading to a complex of twenty temples and chapels, its earliest roots can be traced back to the Middle Kingdom.