用所给词的适当形式填空。

1. My little cat always ________ with the ball in the room. (play)

2. My bedroom is on the ________ floor. (one)

3. How many ________ are there in your home? (study)

4. She is ________ to me. (friend)

5. My father goes to the ________ pool every afternoon. (swim)

男孩，12岁。跌跤后当晚自感全身不适，发热，左膝部疼痛，经用青霉素3日无效来院。检查左股骨下端肿胀，有局限性深压痛，膝关节内有积液，活动障碍，体温39．5℃，白细胞计数18x109／L，分类中性粒细胞占0．9，血沉80mm／h，诊断

A．创伤性膝关节炎

B．股骨下端化脓性骨髓炎

C．化脓性膝关节炎

D．股骨下端骨肉瘤

E．风湿性膝关节炎