Choose the letter A, B, C or D to complete the sentences with given words

The/ biggest problem/ for/ humans/ live/ other planets/ be/ lack/ atmosphere and water.

A. The biggest problem for humans to live in other planets is lack of atmosphere and water.

B. The biggest problem for humans living on other planets is lack of atmosphere and water.

C. The biggest problem for humans to living in other planets is lack of atmosphere and water.

D. The biggest problem for humans to live on other planets is lack of atmosphere and water.