在横线上填上合适的数．

3个 $\frac{1}{8}$ 是____．

$\frac{7}{9}$ 里有____个 $\frac{1}{9}$ ．

$\frac{5}{12}$ 是____个 $\frac{1}{12}$ ．

如图所示，若开关S闭合后，灯L₁、L₂均不亮，小华同学利用一电流表去查找电路故障，当她将电流表连接在灯L₁两端时，电流表没有示数，将电流表接在灯L₂两端时，电流表有示数，由此可以判断 （    ）

根据所给句子选出相应的职业

teacher　　doctor　　farmer    driver    policeman

①I work in a hospital. I help people. I am a ____．

②I work on the farm. I get many good things in autumn. I am a ____．

③I drive a bus every day. I can travel. I am a ____．

④I work at school. I love my students. I am a ____．

⑤I am very busy. I catch the thieves(小偷)．I am a____．

30+40－20=____

5+60－5=____

90－50－40=____