When germany began world war ii in 1939, a secret agreement with the u. s.s. r. allowed soviet troops to
occupy eastern poland
annex eastern czechoslovakia
gain control of the straits of the dardanelles
annex romania

The correct answer is "occupy eastern Poland'. This was called the Ribbentrop-Molotov Pact, named  after the foreign ministers of the two countries, which was a treaty in which the two powers divided Europe among themselves.

Very useful. it is to learn because history repeats itself so learning about it those mistakes not happen again.