设有员工实体Employee（employeeID，name，sex，age，tel，departID），其中employeeID为员工号，name 为员工姓名，sex 为员工性别，age 为员工年龄，tel 为员工电话（要求记录该员工的手机号码和办公室电话），departID 为员工所在部门号（要求参照另一部门实体Department 的主码departID）。 Employee 实体中存在的派生属性及其原因是 （） ；Employee 实体中还存在多值属性，该属性及其该属性的处理为 （） ；对属性departmentID 的约束是 （） 。
Employee实体中存在的派生属性及其原因是（）
A．name，会存在同名员工
B．age，用属性birth 替换age 并可计算age
C．tel，员工有多个电话
D．departID，实体Department 已有departID
参考答案：B
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| Jack 1 in the country and he loves 2 in the river near his house, but his father gets a job in a big city and he moves there 3 his family. Their new house has a garden, but the garden is small. Jack 4 very happy. "Is there a river 5 here?" He is asking his mother 6 the first morning. His mother is answering, "No, there isn't, but there is a beautiful park nearby and there is a pool in it. We 7 there this afternoon." Jack is happy now. After lunch, Jack and his mother go to the park. Jack wants 8 near the pool, but there is a sign in front of it. His mother reads it to him. "Warning (注意), this pool is dangerous, 367 people have fallen into it (已掉入)." Jack looks into the pool 9 and he says, "But I can't 10 them." | ||||
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