Because of high demand for Type AB blood, supplies of it are usually limitedA. the; the

Because of high demand for Type AB blood, supplies of it are usually limited．
A. the; the
B. /; /
C. /; the
D. a; the

A. the; theB. /; /C. /; the(答案→)D. a; the解析：考查冠词的用法。句意“由于AB型血需求量大，它的供应通常有限。”表示泛指用a/an；表示特指用the。第一空表泛指，用a；第二空特指AB型血的供应，用the。故选D。

我也是这个答案