If $$a, b, c, d$$ and $$p$$ are distinct real numbers such that $$(a^2+b^2+c^2)p^2 - 2p(ab+bc+cd) + (b^2+c^2+d^2) \le 0$$, then

A

$$a, b, c, d$$ are in A.P.

B

$$ab = cd$$

C

$$ac = bd$$

D

$$a, b, c, d$$ are in G.P.