设语言L={w|w∈{a,b}⁺且w中a和b的个数相等}，产生语言L的上下文无关文法是(28)。

(88)

(89)

(71)data　effectively　is　crucial　for　success　in　today's　competitive　environment.　Managers　must　know　how　to　use　a　variety　of　tools.　Integrated　data　takes　information　from　different　sources　and　puts　it　together　in　a　meaningful　and　useful　way.　One　of　the　difficulties　of　this　is　the(72)in　hardware　and　software.(73)integration　uses　a　base　document　that　contains　copies　of　other　objects.(74)integration　uses　a　base　document　that　contains　the　current　or　most　recent　version　of　the　source　document　it　contains.(75)provides　an　overview　of　the　program　written　in"　plain"　English,　without　the　computer　syntax.

(86)

(87)

(83)

(84)

(81)

(82)

(78)