After he was knocked down by a bike, he was badly hurt and had to ________to his feet.

[      ]

A. stand 　　　　　　　

B. struggle　　　　　　　

C. run　　　　　　　

D. sit

能将(NH₄)₂SO₄、K₂SO₄、NH₄Cl、KCl四种溶液鉴别开的试剂是  

A．NaOH溶液

B．Ba(OH)₂溶液

C．BaCl₂溶液

D．AgNO₃溶液