21. While he was ______ about in the street, Mary came up to him.
A. wandering B. wondering C. wondered D. wandered
22. Problems _____ because they were lack of communication.
A. raised B. rose C. arose D. aroused
23. Specialists may be useful to _____ a situation and suggest solutions.
A. analytical B. analyze C. analysis D. analyst
24. The conference had been held to discuss the effects of tourism ___ the wildlife in the rainforest.
A. in B. on C. at D. with
