单选题

function Foo(){} Foo.proto...

Question

function Foo(){}

Foo.prototype.z = 3

var obj = new Foo()

console.info(obj.z)

obj.z = 10

console.info(obj.z)

delete obj.z

console.info(obj.z)

请选择正确的输出值

A. undefined10 10

B. 3 10 undefined

C. 3 10 3

D. 都不正确