口腔黏膜局部缺损深达肌层，该病变属于
A．瘘管B．溃疡C．窦道D．糜烂
参考答案：B
You made the same mistake for ______ third time , dropping _____ “r” in the word “ government” .
A. a, the B. a , an C. the , an D a, a
凝胶过滤法是依赖（）来分离蛋白组分。
A、分子大小
B、带电状态
C、分子质量
D、解离状态
