Деревянко, 7. Учебник. Unit 8. Lesson 6

Yes, we know who build the Pyramids.

I think the Pyramids were built by Egyptian (aliens).

The famous archaeologist thinks that the Pyramids were built by Egyptian.

I don’t believe (that) Egyptian built the Pyramids. I think they didn’t know mathematics.
I think you are wrong. Scientists can Explain how the Pyramids were built.

(возможные варианты)
Dear “Young Scientist”,
Lindsay thinks that aliens built the Pyramids. But I don’t agree with her. I don’t think that they built the Pyramids. How could aliens do it? Why the Egyptian couldn’t do it. Finally there are a lot of evidences that it was Egyptian.
Yours Mike.