Directions: Beneath each of the following sentences there are four choices marked A, B, C and D. Choose the one answer that best completes the sentence.
21. Not getting enough vitamins can cause serious diseases. Long ago sailors _______ long sea voyages did not have fresh food. They suffered from a disease called scurvy(坏血病).
A. on B. for C. with D. to
22. My friend devoted most of her spare time when she was living in English ________ scientific research on genetic science.
A. to make B. making C. to making D. make
23. The duck served in that restaurant ________ especially good with excellent flavor is always in great demand.
A. to taste B. tasting C. tasted D. to be tasted
24. Dictionaries of this kind are without doubt convenient tools _________ students of English frequently refer when doing reading.
A. as B. which C. with which D. to which
25. The traffic police had just handled a serious accident on the highway No. 118 ______ another accident occurred somehow.
A. since B. while C. where D. while
26. Clothes made of materials like nylon ________easily and are quite cheap to buy.
A. dries B. dry C. are dried D. can dry
27. I wonder how long it will be ________ man is able to get rid of horrible diseases like cancers, AIDs and heart
