Определите основную идею текста
Most textbooks on Geology of the 20th century dealt with the plate tectonic activity.
The 20th century is the century of discoveries in all fields of science.
Last century gave rise to many theories about the mountain origin and evolution.
Careful study of the textbooks on Geology allows to see the evolution of the mountain origin theory and the final conclusion the scientists of the 20th century came to.