题目

  We all hold such a point that _______ good knowledge of English is what is needed badly in ______ international trade today. A. a ; /                                  B. the ; the                          C. the ; an                  D. / ; the 答案：A将硝化细菌接种到下列培养基中，其中可以长出硝化细菌菌落的是(　　)。A. 无氮培养基，试管密闭B. 无氮培养基，试管口用棉塞塞住C. 含氮培养基，试管密闭D. 含氮培养基，试管口用棉塞塞住