Answer:
The first part of this sentence is a fact, the second part is an opinion.
Step-by-step explanation:
The reason why the second part is an opinion is because workers built the tombs, not the pharaohs. It is correct where it says the tomb were built for the pharaohs, but it wasn't by themselves; in fact, they didn't even do any of the work on the tombs, they just saw the progress of it.