The _______ method of an Array object adds and/or removes elements from an array

Which of the following function of Array object applies a function simultaneously against two values of the array (from right-to-left) as to reduce it to a single value?

In this example, what would the VALUE of employee.functions[1] be?

{ "employee" : { "type" : "Director", "functions" : ['sales', 'marketing'] } }