The correct answer is A.
The fact that Egyptians used geometry to determine their boundaries is not explicitly stated in the passage. However, it can be inferred from the passage that yes, the Egyptians did use geometry to define their boundaries.
We can infer this information because the passage tells us the Greeks were not the first to use geometry. The Egyptians used geometry well before the Greeks. Finally, the last line of the passage indicates that defining boundaries "was certainly a practical use for geometry."
Therefore, the correct answer is A. It is true that the Egyptians used geometry to determine their boundaries.