A.5 B."5" C.undefined D.null
A.Math.max(arr) B.Math.max(arr[0],arr[1],arr[2],arr[3]) C.Math.max.call(Math,arr[0],arr[1],arr[2],arr[3]) D.Math.max.apply(Math,arr)
A.Object.length() B.String.prototype.split() C.Array.prototype.join() D.Promise.all()