Answer:
It is less dense than oxygen gas.
Explanation:
Density is a physical property. Reactivity, flammability, and acid compounds are all chemical properties.
Hope that helps.
The Lewis bases are those which can donate electron pair to an acceptor. These electrons can be a pair of electron that is a lone pair, a negative charge or electrons in a 
-bond.
- In
, the presence of -bond make it a Lewis base. - In
, the presence of negative charge makes it a Lewis base. - In
, the presence of lone pair on nitrogen makes it a Lewis base. - In
, there is no lone pair, no -bond, no negative charge so it is not a Lewis base.
Hence, , , and are Lewis bases.
