5. (2.0分) ___ in his speech was the assumption that they were guilty.A. ImageB. ImplicitC. ImpactD. Imaginary

本题考查词汇辨析，解题思路是理解每个选项单词的含义，再结合句子语境来判断哪个选项能使句子语义通顺合理。

• A选项“Image”：作名词时，意为“形象；影像；图像”。若将其代入句子“___ in his speech was the assumption that they were guilty.”，句子表达“在他的演讲中形象是他们有罪的假设”，语义不通顺，所以A选项不符合。
• B选项“Implicit”：作形容词，有“含蓄的；内含的；无疑问的”等意思。“Implicit in his speech was the assumption that they were guilty.” 这句话可以理解为“他的演讲中含蓄地表达了他们有罪的假设”，语义合理，符合语境，所以B选项正确。
• C选项“Impact”：作名词时，意为“影响；冲击力”；作动词时，意为“影响；冲击”。把它代入句子，“在他的演讲中影响是他们有罪的假设”，语义不恰当，所以C选项不正确。
• D选项“Imaginary”：是形容词，意为“想象的；虚构的”。代入句子“在他的演讲中想象的是他们有罪的假设”，语义混乱，不符合逻辑，所以D选项不合适。