In reference to the futures market, a "speculator" _______.
A.
attempts to profit from a change in the futures price
B.
wants to avoid price variation by locking in a purchase price of the underlying asset through a long position in the futures contract or a sales price through a short position in the futures contract
C.
stands ready to buy or sell contracts in unlimited quantity
【简答题】The computer warning system keeps track of a driver's condition by monitoring his heart beat with signals transmitted from a band round his wrist which records the driver's _______.