The increased ranges of plant and insect species resulting from climate change has only negative consequences.

False, it has also positive consequences for other specie advantages. 
Like any other change, it has a both positive and negative effect on the said biosphere, ecosystem or the entire living organisms that exists and co-exist. Climate change maybe is one of todays greatest selection and environment forces that reforms a lot of living organism and especially the climate. 

The correct answer is  b) 

Control variable- changedependant variable- stays the samechanging- food itemsdependant- presences of proteins