Roads in the ____ (mountain) area have been badly damaged by the earthquake.
30+5=____ 40+8=____ 77-7=____ 64-0=____
32-2=____43+0=____ 90+9=____ 10+7=____
在含有大量Na+、H+、Cl﹣的溶液中,还可能大量存在的是( )