Liquids and gaseous fuels have more advantages over solid fuels. Some advantages are:
(i) Calorific value of liquid and gaseous fuels is higher than solid fuels.
(ii) Liquids and gaseous fuels have higher ignition temperatures than solid fuels.
(iii) Liquids and gaseous fuels are easier to store since solid fuels occupy a lot of space.
(iv) Liquids and gaseous fuels burn completely, leaving no residue.
The correct advantages are:

A spoon is kept in contact with ice cubes for some time. Later, the same spoon was held over the flame of a small candle. The observation is shown in the figure. What do you infer from the given figure?

Calorific values of some fuels are given:

On the basis of this data, find out the correct order of efficiency of fuels.

Different zones of a candle flame are marked by the letters $P,Q,R$   and $S$.
Which of the following statements are correct?
(i) $P$ is the luminous zone and is the hottest part of candle flame.
(ii) In zone $Q$, there is inadequate supply of oxygen.
(iii) Zone $R$ contains unburnt wax vapours produced by melting of wax.
(iv) In $S$ zone, carbon monoxide burns with a blue flame.

Neha took a burning candle and covered it with an empty glass by putting it upside down. She observed that the candle burns for some time before it finally goes off. What is the reason for this?