how we can calculate the order of group that i know, but Question is this

 

 

A abliean group of order 28

 

(a) has exactly two subgrop of oredr 3

(b) no subgroup of order 3

© more than two subgroup of oredr 3

(d) one sub group of order 3

 

what will be the correct answer among these?

 

Thanks for answer..................

You'll be wanting to use Sylow's theorem for this. It's such an easy application that I don't really want to do it for you.

You don't even need the full blown Sylow theorems. You just need Lagrange's theorem.