21. It is believed that traveling to Yangzhou in ________ March is ________ enjoyable experience.
A．/；/ B．the；an C．/；an D．/；the
22. To learn English well, we should find opportunities to hear English _____ as much as we can.
A. speak B. speaking C. spoken D. to speak
23. This is the town________ we visited last year.
A．who B．in which C．which D．in that
