What event opened asian nations, particularly china, to trade with europe?

the opium wars
word war i
the sino-japanese war
the russo-japanese war

List three reasons why explorers began to explore new, and old areas. [[ps: doesn't explicitly say where. i think it's more in general.

Why was it difficult fpr unions to succeed in the 1800s

In the 1980s, more russians worked to encourage change in the government by a) establishing a new political system. b) rallying for democratic reforms. c) supporting the democratic system. d) resisting gorbachev’s reforms.