Which definition best describes global warming?
a. a long-term change in the earth's climate
b. a long-term increase in the earth's average temperature
c. a long-term change in the climate of a region or a city
d. solar heat that is radiated out into space

 B a long-term increase in the Earth's average temperature

B

Explanation:

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

carbon

explanation: