Compound A reacts with alcoholic KOH to yield compound B which on ozonolyzises followed by the reaction with Zn/H2O gives methanal and propanal Compound A is

1-chlorobutane

Explanation:

Given that :

-- The compound A is made to react with alcoholic KOH and produce compound B.

-- The compound B on Ozonolysis produces methanol as well as propanol

The compound A should be a haloalkanes as treatment of haloalkanes with the alcoholic KOH, it will give alkene.

So, the compound B should be Butene

Now the ozonolysis of the compound B or butene will give methanol and propanal as shown :

Therefore, the compound A is 1-chlorobutane.

1.solid

2.carbon dioxide

3.helium

it means there are 3 atoms of oxygen