Which of the following is not a theory supporting global warming?

What following?

a.

It is predicted that the average temperature will rise 1.4° C or more over the next 100 years.

b.

Human activity has increased greenhouse gases.

c.

Over the last 100 years the earth has warmed by 0.74° C

d.

Carbon dioxide is an insignificant greenhouse gas.

Explanation:

d.

Carbon dioxide is an insignificant greenhouse gas.