下列哪种蛋白质含量减低可引起水肿（ ）
A．补体
B．清蛋白
C．免疫球蛋白
D．甲胎蛋白
E．纤维蛋白原
参考答案：B
Making friends is not easy. Sometimes it can take years you become true friends with someone.
A．before
B．after
C．because
D．Unless
