So far, more than 1300 hotels in Europe, Africa, Middle East region have committed to _________ in the event, with many more ________ to join the effort.

A．participating; expecting

B．participate; to expect

C．participating; expected

D．participate; to be expected

流行性腮腺炎主要临床特征是（），常见并发症为（）、（）、（）。