The actual ba is created at a late stage in the underlying transaction when a bank accepts its obligation to pay the holder of the accepted draft.
在银行承担了为已承兑汇票的持有人付款的义务时，实际的银行承兑就发生了。
2
A call is option that gives the buyer the right, but not the obligation, to purchase the underlying futures contract at the strike price on or before the expiration date.
看涨期权赋予买方以权利，但不必负有义务，在期权到期日当天或到期之前，按敲定价格买进相关期货合约。
3
The seller of the option has the obligation to buy the underlying instrument if the holder exercises the option to sell.