选出与所给单词同类的一项。
(______) 1. farm A. worker B. hospital C. black
(______) 2. interesting A. potato B. blackboard C. useful
(______) 3. thirty A. forty B. first C. second
(______) 4. kind A. cross B. easy C. take
(______) 5. cousin A. brother B. which C. should