Which statements are true of fossil fuels?
check all that apply.
a. the burning of them contributes to global warming.
b. they produce harmful waste.
c. they come from water.
d. they are renewable.

Letters A and B are correct because burning fossil fuels can harm the atmosphere through the greenhouse effect and contribute to global warming, and can sometimes spill into the water and harm the environment.

The ratio is 3: 2. i.e. c.

Electron equations of the given changes are as follow,a)                              cu      →      cu⁺²  + 2e⁻b)                              mg⁺²  +  2 e⁻      →      mgc)                              cl⁻    →      cl  +  1e⁻d)                              s  +  2 e⁻    →      s²⁻e)                                o²⁻      →      o  +  2 e⁻f)                              p  +  3 e⁻    →      p³⁻g)                              fe²⁺    →      fe³⁺  + 1 e⁻h)                              s²⁻    →      s⁴⁺  +  6 e⁻