Indian Institute of Foreign Trade 2015 Solved Paper

(a) Going through options
Let p = 1, q = 2 and r = 3
Clearly p, q and r and in A.P
Now, r – q = 1, q.p = 1
1, 1, 1, one in G.P
So, p, r – q and q – p are in G.P
So option (a) is correct.