下列物质属于共价化合物的是[ ]

A．NH₄Cl

B．HNO₃

C．H₂

D．Na₂O₂

With the aid from the whole country, the people in the flooded area of northeastern China managed to ______ this unforgettable summer of 2013.

A．go through

B．look through

C．break through

D．rush through