First, it is important to understand the requirements imposed by the key term in the question in terms of what your response should entail. NESA defines the word "assess" as:
Make a judgement of value, quality, outcomes, results or size
Based on this, it can be inferred that your answer needs to constitute relevant judgement according to particular information. Here, perhaps having a look at the marking criteria will enable you to determine the exact components that you need to incorporate as part of your judgement within your response:
- Clearly and correctly links ALL THREE of the colours observed (when the natural indicator was added to solutions A, B & C) to the level of acidity/basicity of each solution. The answer can be either quantitative (eg. pink indicates pH < 3.1) OR qualitative (eg. pink indicates a strongly acidic substance). The answer MUST be consistent with the analysis given in question 2.
- Makes a judgement about the usefulness of red pansy solution as acid/base indicator that is consistent with points 1 and 3.
- Provides ONE (3 marks) or TWO (4 marks) statements supporting the judgement that detail the usefulness of the red pansy solution as an acid/ base indicator (relating colours, & the pH range they indicate, to their ability to identify/distinguish between solutions with different pH’s.)
As you can see, the marking criteria, especially point 2 and point 3, is consistent with NESA's definition of the word "assess" regarding the judgement part. Maximising your marks in such questions will therefore necessitate consideration and attention to such elements in order to not only ensure that information you include in your response is accurate, but that including such information also allows you to effectively respond to the question.
I hope this helps!