Which of the following could have a negative impact on science

Idon’t know how to solve this question

The gulf stream is a warm water current that flows away from the equator to northern europe. witch of these does it cause. a. crashes of warm and cool water in the ocean b.colder climates near the equator c.large waves on the cost of europe d.warm climates in northern europe

State one important difference between a physical change and a chemical change?