Which of the Following Best Explains Why Wind and Solar

Which of the following best explains why wind and solar power have been slow to replace coal- and gas-based energy production?

A) Energy production with coal and gas generates less pollution.
B) Wind and solar energy availability is subject to large fluctuations because of the inability to store the power.
C) Governments have heavily subsidized coal and gas energy plants, but have not subsidized wind and solar.
D) Consumers are largely unwilling to buy power generated from wind and solar.