A．the market is not efficient.
B．too many people go for it.
C．the prices are always fluctuating.
D．few people have the clear insights,

A．profit opportunities remain a very brief time.
B．only experts can grasp the profit opportunities.
C．people without insights don't get much profit.
D．anyone who knows the hot tips can gain profit.

A．Doubtful.
B．Cautious.
C．Consenting.
D．Ironic.