【正确答案】 B

【答案解析】[解析] 画线词rarely为形容词，意为“稀少地”。A项normally意为“正常地”；例：All the airports in the country are working normally today. 今天国内所有机场都运转正常。B项seldom意为“很少；不常”；例：She seldom showed her feelings. 她很少流露她的感情。C项continuously意为“连续不断地”；例：The river flows continuously along the bank. 这条河沿着河岸绵绵不断地流着。D项usually意为“通常”；例：Influenza usually breaks out in winter. 流感常于冬天爆发。故选B。