Nuclear fission produces about one-fifth the power in the united states. an unintended negative consequences of nuclear power has been that a) a lot of power is generated. b) radioactive waste is created. c) less greenhouse gases are created. d) a peace time use for fission was found.

First, let's see whether all the options are true: 

A) a lot of power is generated - yes, tue, that's what fisssion does!
B)radioactive waste is created - this is the waste produced in nuclear power plants, and it's redioactive material
C)less greenhouse gases are created - this is also true, as the more power we produce through nuclear fission, the less we need to burn fossil fuels
D)a peace time use for fission was found - also true, as nuclear fission can be used to make weapons and also to produce power during peace time!

so all the options are true and we can't reject any for being false. 

now, which one is a negative consequence? more power and less greenhouse gasses are desirable - it would be good for our environment. 

The correct answer is B)radioactive waste is created.  - radio active waste is dangerous for health (it increases the rates of cancer in the area). There are a lot of discussions where to store it, but since  every area refuses to store it because it does not want to endanger its citizens, a lot of radioactive waste is stored at the facilities, often not in the right containers.