【正确答案】 B

【答案解析】[解析] 画线词的原形postulate为动词，意为“假定”，A项的原形challenge意为“挑战”；例：They had challenged and beaten the best team in the world.他们曾向世界上最强的球队挑战并将它打败。B项的原形assume为动词，意为“假定，设想”；例：I assumed you can speak French fluently.我以为你能讲流利的法语。C项的原形deduct意为“扣除，减去”；例：Nowadays income tax is normally deducted from a person's wages.现在，所得税通常是在发工资前就已经扣除了。D项的原形decree意为“判决，裁定”；例：The committee decreed the movie unsuitable for children.委员会裁定这部影片为儿童不宜片。