【正确答案】 B

【答案解析】[解析] 题意：水泥在中世纪建筑中很少被使用。
句中seldom意为：很少，不常。
A项crudely意为：粗糙地，天然地；不成熟地；例句：This is a crudely carved wooden form．这是一件粗糙的木头雕刻。
B项rarely意为：很少地；罕有地；例句：we rarely see someone go after the health area．我们很少见到有人在健康领域做文章。
C项originally意为：最初，起初，本来；例句：Where are you from originally?你最初是哪里人?
D项occasionally意为：偶尔，间或；例句：He went on talking，occasionally wiping at his face with a towel．他继续说着，偶尔用毛巾擦一下脸。故选B。