既能与盐酸反应，又能与NaOH溶液反应的是[ ]

①Na₂SiO₃ ②Al(OH)₃ ③SiO₂ ④Al₂O₃ ⑤NaHCO₃

A．①②④

B．②④⑤

C．②③④

D．全部

She was depressed and began to _       things _      .      [ ]

A. let ;  slide            

B. slide ;  in    

C. let; sliding            

D. slide; over