Usually，polymerization includes_, based on the mechanism involved in forming polymers（）
A. Chain growth polymerization
B. Condensation polymerization
C. Addition polymerization
D. Step growth polymerization
The repeating units on the copolymer chain may be arranged in various sequences along the backbone chain, including（）
A. Random copolymer
Block copolymer
C. Graft copolymer
D. Alternative copolymer
For the molecular weight distribution, which one of the followings is not correct（）
A. There is a considerable variation in molecular weight of polymers
B. The molecular weight distribution can be expressed by the ratio Mw/Mn
C. A polymer sample can be considered as a mixture of chains having different lengths
D. The molecular weights of polymers are usually uniform
学生表student包含学号sno、学生姓名sname、性别sex、年龄age、所在院系dept、籍贯native等字段，其中age为整型，其余字段均为字符型。现插入一条计算机学院学生的记录，学号为s320078，姓名为张强，性别为男，年龄为20，下列语句错误的是__（）
A. INSERT INTO tb_student （sno, sname, sex, age, dept, native） VALUES（‘s320078’, ‘张强’,’男’,20, ‘计算机’）
B. INSERT INTO tb_student （sno, sname, sex, age, dept） VALUES（‘s320078’, ‘张强’,’男’,20, ‘计算机’）
C. INSERT INTO tb_student VALUES（‘s320078’, ‘张强’,’男’,20, ‘计算机’,null）
D. INSERT INTO tb_student （dept, sno, sname, sex, age） VALUES（‘计算机’, ‘s320078’, ‘张强’,’男’,20）
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