The government has introduced an ad valorem tax on petrol. The likely effect is: A) Increase in sales of petrol B) Increase in carbon emissions from electric cars C) Increase in demand for bus travel D) Decrease in sale of electric cars

Four mark questions are a great way to pick up marks. There is a simple strategy to remember when answering these. 

Firstly, always write down your definition of the key word(s). Even if you do not know the correct answer, remembering to write down your definition will gain you a mark or two.

Secondly, if unsure which answer it is, narrow down your choices. In this answer, it is clear that option D will not happen as it is a subsitute for petrol fueled cars. Option A is also not a suitable option as a VAT will make it more expensive to buy petrol resulting in a fall of sales. Option B is also not an option as electric cars will not release carbon emmissions. Correct answer: C

Through this process you are able to pick the right answer or narrow it down to two options which you may feel is right.

Also, adding a diagram will also help you answer four  mark questions. Often diagrams are awarded marks and help you map out what the question is telling you so you can pick the right option.