(3) Given $p: a, b, c, d$ form a geometric sequence, $q: a d=b c$, then $p$ is ( ) of $q$.
(A) Sufficient but not necessary condition
(B) Necessary but not sufficient condition
(C) Sufficient and necessary condition
(D) Neither sufficient nor necessary condition
(3) A Hint: Sufficiency obviously holds, necessity does not hold. Example: $a=1, b=2$, $c=5, d=10$.