【单选题】In the late 1960's, many people in North America turned their attention to environmental problems, and new steel-and-glass skyscrapers were widely criticized. Ecologists pointed out that a cluster of ...
A.
discuss the advantages and disadvantages of skyscrapers
B.
compare skyscrapers with other modern structures
C.
describe skyscrapers and their effect on the environment
D.
illustrate various architectural designs of skyscrapers