A ______ is a growth of feathers, fur or skin along the top of the heads of some animals, especially birds.

【正确答案】 A

【答案解析】 从后面解释“长在动物，尤其是鸟类头顶的毛发”得知，此空为“鸟冠，羽冠”之意，填crest。crust面包皮；硬的外层。crush做名词解，意为“拥挤的人群”。crumb碎屑。