慢性肾功能衰竭出现胃肠道症状的常见原因是（）
A.尿素刺激消化道
B.代谢性酸中毒
C.严重贫血与出血
D.钙磷代谢障碍
E.继发感染
参考答案：A, B
"Whose T-shirt is this?" "It_____ be John's. It's much too small for him.”
A. might B. can't C. needn't
论述建构主义学习理论的基本观点。
