Question

The great pyramids at Giza are remarkable structures because __________. A.they are still the most massive structures ever built by human effort
B.engineers have not figured out how they were built without modern technology
C.. they were the tallest man-made structures until the 20th century
D.they were the most massive man-made structures until the 20th century

Answer 1

i think engineers have not figured out how they were built without modern technology.

Answer 2

thanks