Timing 30 minutes.
Volume more than 250 words.
Evaluating criteria: cohesion and coherence, ability to communicate the idea, solving a communication task.
Read the question attentively - it's a task, in which you will either have to choose or contrast things. You will have to do it based on your opinion, supported with arguments and examples.
Basically, you may write your opinion in the introduction, but there is para 1.
Whereever you express your oinion if you asked for, make sure you solvethis communication task and your essay contains the answert to the question.
If you are asked to choose, you have to write your choice. If you are asked to compare, there have to be language instruments of comparison. If you are asked to express your opinion, do it, but such tasks tend to be finalised with your choice and supporting arguments/reasoning.
The structure could be so that you express your opinion in the introduction and you provide reasons and all the rest in the following paragraphs. So, no matter in which paragraph you write your opinion, if you are asked for one, make sure your essay contains your opinion.
There has to be a conclusion.