单选题

上面这段代码运行后的输出是:

Question

(function() {
      var a = b = 5
  })()   
console.log(b)
console.log(a)

上面这段代码运行后的输出是:

A. 5，5

B. undefined，undefined

C. 5，undefined

D. 5，Uncaught ReferenceError: a is not defined