The first molecule is a sensible molecule having complete octet of each atom such as C, H and O whereas the second molecule having hydrogen present between the aldehyde and methyl group and thus showing hydrogen is making bond with aldehyde and methyl as well which is not possible because hydrogen only having one electron in its octet due to which it can only form a single bond by sharing its valence electron.
CH4 is <u>not</u> soluble in water
whereas CH3OH <u>is</u> soluble in water.
The 2 represents that it is a double carbon bond
it looks like..
C-C = C-C
The question ask to predict the effect where as coal can be used to generate hydrogen gas by this endothermic reason and the best answer among your choices based on the element you give is letter C. raising the temperature of the reaction mixture. I hope my answer is correct