Although temperatures have fluctuated throughout the earth's history, scientists are greatly concerned about the current warming because

This rate tends to be faster than in most other periods. The rates in previous eras was very gradual and did not have as much of a deleterious effect on the life that was present: today's rate is much more rapid and has the potential to do much more damage to the life on the planet.

Ithink you should go back and learn in school rather then here asking questions

Ibelieve is d but i’m not 100% sure