21 （2011·山东潍坊高三质检）Because of ______high demand for Type AB blood，____supplies of it are usually limited．
A．the；the B．不填；不填 C．不填；the D．a；the
22 （2010·安徽省安庆一中三模）4. Yesterday was the twins’ birthday, ________ presented a gift.
A each of them B each of whom C both of them D both of whom
