问题补充:
----- In recent years, problem of global warning has been very serious.
------That’s right. People are facing number of natural disasters now.
A. 不填;
B. a; the
C. the; a
D. a; a
答案:
A. 不填;
B. a; the
(答案→)C. the; a
D. a; a
解析:考查冠词。全球变暖的问题是特指,a number of,许多,为固定表达。