He ______ dinner at restaurant, but now he usually comes back home after work and cooks supper for his family.

A．used to have

B．is used to have

C．was used to have

D．is used to having

保证金制度指在期货交易中，任何交易者必须按照其所买卖期货合约价值的一定比例（通常为5%～10%）交纳资金，用于结算和保证履约的制度。（）