Hi,
just in advance: am sorry in case I offend anyone. But:
The question is utterly stupid, as it indicates, that the "leading" cause for Physiotherapy input relates to the assessment and treatment of pain.

And in case, you have to answer the question, as part of an exam: answers 1 & 2 are part of your subjective assessment, answer 3 is an outcome measure. Of cause they are all equally important, but why would you use an outcome measure before you even know exactly what you refer to?
Cheers,
Fyzzio