【正确答案】 C

【答案解析】[解析] 画线短语in the end为副词短语，意为“最后，最终”。A项undoubtedly意为“确实地，毋庸置疑地”；例：It has undoubtedly led to many exciting developments.它的确取得了许多令人兴奋的进展。B项certainly意为“当然，必定”；例：I"m certainly going, but I"ll be a little bit late.我去是去，可是得晚一点儿。C项ultimately意为“最后，根本上”；例：I believe we are ultimately going to be successful.我相信我们最后终将走向胜利。D项necessarily意为“必要地，必然地”；例：The study of foreign language is necessarily difficult.学习外国语言必然困难。故本题选C。