Oxygen is in group 16 of the PTOE, so it has 6 valence electrons. In order to have a full outer shell it would need 2 more electrons. (second shell can hold a max of 8 electrons)
Answer: B) combustion reaction.
Explanation:
A) acid-base reaction: When an acid reacts with a base, to form metal salt and water, this type of reaction is Acid Base reaction.
Example: 
B) combustion reaction: When a hydrocarbon reacts with oxygen to produce carbon dioxide and water, this type of reaction is combustion reaction.

C) precipitation reaction: a reaction in which aqueous solution of two compounds on mixing react to form an insoluble compound which separate out as a solid are called precipitation reactions.

D) gas evolution reaction: a reaction in which one of the product is formed as a gas.

I guess you are asking what world should go at the beginning of the sentence. If I am right, it is energy.
Answer:
The water will evaporate and fly out of the bucket; the process will not stop until there is enough water vapor in the atmosphere that the vapor pressure stops the water from boiling further.
Explanation: