用薄钢板加工如图所示的零件，以下加工流程合理的是（   ）

电热水袋中的水加热后袋子膨胀，是因为袋内的水（   ）

有4种混合溶液，分别由等体积0.1mol/L的2种溶液混合而成：①CH₃COONa与HCl；②CH₃COONa与NaOH；③CH₃COONa与NaCl；④CH₃COONa与NaClO 下列各项排序正确的是（   ）

     Two men are walking in the park. One is Mr Brown , a worker, the other is Mr Black. Mr Brown is going to a chair. It is by the road. Mr Black is after him. Mr Brown finds Mr Black. Now Mr Black begins to walk faster(更快). Because he wants to get to the chair before Mr Black. Now Mr Black begins to walk faster because he also wants to get to the chair first. Then they both run .Mr Black runs faster than (比) Mr Brown. So he gets to the chair first and sits down on it. Mr Brown runs after Mr Black. When he gets to the chair. He sees Mr Black sitting on it. He is sorry to show a notice(通知)with the words“Wet Paint(油漆未干)”to Mr Black . Now Mr Black knows why Mr Brown is going to the chair.

已知函数f（x）= $\frac{\left|x\right|}{x+2}$ ﹣kx²（k∈R）有四个不同的零点，则实数k的取值范围是（   ）