A.抽象性B.遞歸性C.系統(tǒng)性D.穩(wěn)定性
A.他們寫(xiě)毛筆字B.他們寫(xiě)了毛筆字C.他們寫(xiě)起毛筆字來(lái)D.他們寫(xiě)著毛筆字
A.learnB.be learningC.learnedD.have learned