Someday software will translate both written and spoken language so well that the need for any common second language could ________.
句意：有一天软件会将书面和口头语言翻译得非常好，以至于对于任何一种通用的第二语言的 需求将会下降。decline减少；衰落。descend下降；下去。deteriorate恶化，变坏。depress压抑；使沮丧。故选B。