An area where the earth's crust would be expected to be thin would be

under the pacific ocean
in the rocky mountains
under the mississippi river
in the plains region of the midwestern u. s.

The best and most correct answer among the choices provided by the question is the first choice. The crust is expected to be thin under the Pacific Ocean. I hope my answer has come to your help. God bless and have a nice day ahead!

C) to ensure each new cell has an exact copy of the dna