A: "number"

B: "array"

C: "object"

D: "NaN"

A: function language(lang) { this.languages.push(lang }

B: 0

C: []

D: undefined

a) [1, 1, 2, 3, 4]

b) {1, 1, 2, 3, 4}

c) {1, 2, 3, 4}

a) 2

b) 18

c) 24

a) "undefined", "number"

b) "number", "number"

c) "number", "undefined"

a) 12

b) 14

c) 20

a) [2, 4, 6]

b) [1, 2, 3]

c) [undefined, undefined, undefined]

a) 10

b) undefined

c) TypeError

a) true

b) false

c) undefined

a) "class"

b) "function"

c) "object"

a) Hello, Alice!

b) Hello, name!

c) Hello, undefined!