The temperature decreases because there is no ozone in the mesosphere and the amount of air is decreasing.
Element: Boron
Symbol: B
So answer is B
Explanation:
The structures of both acetone and propanal are shown below:
In the formula of propanal there is -CHO functional group at the end.
In acetone -CO- group is present in the middle that is on the second carbon.
The molecular formula is C3H6O.
Both have same molecular formula but different structural formulas.