急性牙槽脓肿是指（）
A.根尖肉芽肿
B.根尖周炎急性浆液期
C.根尖周炎急性化脓期
D.急性牙周膜炎
E.牙周脓肿
参考答案：C
下列哪项不是噬菌体的特征（）。
A.个体微小
B.具备细胞结构
C.由衣壳和核酸组成
D.专性细胞内寄生
E.以复制方式繁殖
They will come to help us with the harvest ______ they are busy tomorrow. [ ]
A. even if
B. however
C. as though
D. even although
