Dense fog is covering roads in the north and visibility is very poor.

参考答案: B

参考解析: 本句意思是：浓密的雾笼罩了北部的道路，能见度很差。句中dense是形容词意为“浓密的”，例如：They thrust their way through the dense crowd.他们挤过密集的人群。四个选项中：obscure意为“模糊的”，例如：The contracts are written in obscure language.这些合同的语言晦涩难懂。impenetrable意为“密的、看不透的”，例如：I had also judged the jungle of both banks quite impenetrable.我先前早已留神了，两岸的丛林异常茂密，一眼看不透。condensed意为“缩合的、冷凝的”，例如：My favorite is condensed mushroom soup.我喜欢蘑菇浓汤。 sparse意为“稀少的”，例如：Traffic was sparse on the highway.公路上车流稀少。只有选项B同句中画线单词含义接近。