Of the molecules below, the bond in is the most polar. hbr hi hcl hf

There's a trend in electronegativity. The bottom left of periodic table is the lowest (0.7) and the upper right is the highest (4.0). The most polar is the greatest difference in electronegavity. hbr- 1~ , hi- 0.5~ ,hcl - 1.3~ , hf-1.8 so,hf is the answer

The gas would begin to expand, and eventually the can would burst or explode.