15.
Read the text below. For each empty space (1-6) choose the correct answer (А, В, C or D).
Planet Earth is a ball of rock and metal, (1) __________________ up of four layers. The thin, cool, out¬side layer (2) __________________ the crust. People live on the surface of the crust. The three layers inside (3) __________________ and (4) __________________ than the crust. No one (5) __________________ exactly what earth is like deep inside, but we do know that (6) __________________ part is in the middle.

A В C D
1 made make making was made
2 called calling calls is called
3 is thicker are thicker is thickest are thickest
4 more hotter much hot much hotter more hot
5 knows know is known known
6 hotter hot the hotter the hot