I need the answer for rebuttal help me pls pls pls

Which events are correlated but do not necessarily have a causal relationship?

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.

What from the columbian exchange had perhaps the biggest impact on the world?