题目

You must register for the conference before or at the same time as submitting a hotel reservation form. Reservations without a registration will not be processed. ROOM RATES/TAXES To take advantage of the special TESOL rates, please book your reservation by February 20, 2016. After that date, TESOL room blocks will be released and reservations will only be accepted at the conference rate based on availability. All rates are per room per night and £ire 15. 2% tax. CHANGES/CANCELLATIONS All changes/cancellations can be made through February 25, 2013 via the TESOL Housing Service by Intern15．在煮饺子时，刚下锅的饺子是沉在水底的，开锅后饺子就逐渐浮在水面上，对这一现象的解释中正确的是（　　）A．开锅后，因饺子受热膨胀，密度变大，大于水的密度，所以浮到水面B．开锅后，因饺子的质量变小，重力也变小，重力小于浮力，所以上浮到水面C．开锅后，因饺子里面的空气受热膨胀，使饺子的体积增大，浮力增大而上浮到水面D．开锅后，因沸腾的水中上升的气泡把饺子顶了起来