46.Which statements are correct regarding indexes? (Choose all that apply.)

46.Which statements are correct regarding indexes? (Choose all that apply.)
A.When a table is dropped, the corresponding indexes are automatically dropped.
B.A FOREIGN KEY constraint on a column in a table automatically creates a nonunique index.
C.A nondeferrable PRIMARY KEY or UNIQUE KEY constraint in a table automatically creates a unique index.
D.For each data manipulation language (DML) operation performed, the corresponding indexes are automatically updated.
答案：ACD
解析：
A：正确，索引依附于表，删除后对应的索引也会删除
B：错误，应该是主键或唯一键会自动创建
C：正确
D：正确