Arrange the given words in alphabetical order and select the one that comes in the middle :
Cover , Code , Coin , Core , Count.

Cover , Code , Coin , Core , Count.

Logic: We compare letter of words.  

​Compare 1st and 2nd letters: C and o

C and o are common in all words.

Compare 3rd letter: v, d, I, r and u

d comes before i, i comes before r, r comes before u, u comes before v.

Then, correct order is: Code, Coin, Core, Count, Cover

So, the middle word in this sequence is Core.

Thus, the correct answer is (c).