The correct option is C H.P.
a,b,c are in H.P.
⇒1a,1b,1c are in A.P.
⇒a+b+ca,a+b+cb,a+b+cc are in A.P.
∵ Multiplying an A.P. with a constant (a+b+c), resulting sequence will also be in A.P.
⇒1+b+ca,1+a+cb,1+a+bc are in A.P.
⇒b+ca,a+cb,a+bc are in A.P.
⇒ab+c,ba+c,ca+b are in H.P.