胸腺依赖性抗原的特点是（）
A.抗体类型为IgG
B.不引起细胞免疫
C.免疫原性较强
D.能诱导免疫记忆
E.具有佐剂作用
参考答案：A, C, D
— What did you do yesterday?
— We had great fun in the park. [ ]
A. plays
B. played
C. playing
D. to play
混凝土坍落度检验应在混凝土送到现场后（）分钟内完成。
A.10
B.20
C.30
D.40
