Question

Enumerate the factors that should be considered when choosing a fuel

Answer 1

The type of flame produced by the fuel 2. Amount of heat produced during combustion 3. Effects of products formed 

Answer 2

Ideal fuel is a fuel which when used do not harm environment and is eco-friendly to nature.Example:Cng (compressed natural gas)
Factors to be consider while selecting a fuel are as follow
1. It should be eco-friendly to nature.
2.Does not live residue like petrol which remains carbon monoxide as residue
3.Affordable 
4.Easily get combust

or

The criteria for selecting a good fuel are :-
It should have a high calorific value.
It should have a low ignition temperature but not below room temperature.
It should be easily transportable.
It should be easy to store.

I hope this will help you