过量饮用咖啡对人体的不良影响有（）
A、导致血压升高
B、预防胆结石
C、抑制新陈代谢
D、促进血液循环
参考答案：A
某校操场原有面积2800m2，因扩建，把宽从40m增加到50m，长不变．扩建后的操场面积比原来增加多少m2？
In American, a friend inviting you to a restaurant doesn't mean that he or she will pay for the meal ______ you are told ahead.
A．until
B．unless
C．although
D．if
