Which one of the following is a decomposition reaction? a. k2co3 (s) → k2o (s) + co2 (g) b. 4fe (s) + 3o2 (g) → 2fe2o3 (s) c. n2 (g) + 3h2 (g) → 2nh3 (g) d. 2lioh (s) + co2 (g) → li2co3 (s) + h2o (l)

You would know a decomposition reaction occurred if the reactants separated. For example from AB → A+B.

Now if you look at your options only 1 works out for that equation. Letter A. 
From the compound K2CO3 it split up to K2O +CO2

It cannot be letter B because synthesis/combination occurred. The same goes for letter C. Letter D, single displacement occurred. 

Again, the answer is A.

English can you write this in english do we can you

I’m good with pshycology