Which is true about invalid PL/SQL objects?

　　A)They are automatically recompiled against the new definition of a referenced object when they are called.

　　B)They must be manually recompiled before they can be used if a DDL is performed on a table that is referenced in the PL/SQL object.

　　C)They are automatically recompiled against the new definition of a referenced object at the same time as the referenced object is modified.

　　D)They can be manually recompiled only by using SQL commands.

　　Answer: A

　　赵：

　　A 译：它们在被调用时根据引用对象的新定义自动重新编译。

　　B 译：如果在 PL/SQL 对象中引用的表上执行 DDL，则必须手动重新编译它们才能使用它们。