Well the first part is really up to you to figure out. Literally take a company you are interested in and explain why you’d want to work on that client. It’s not a trick question.
Second part wants you to demonstrate business acumen. You need to show you’ve researched the client and that you are aware of the current state of the economic climate they are operating in. SWOT and PESTEL framework will help you generate insights.
Third part wants you to demonstrate that you are knowledgable in the services PwC offer and how they add value for the client. Again this just requires doing some research and understanding how PwC’s services benefit businesses.
E.g. Tax department could offer advice to optimise tax structure or ensure full compliance with HMRC regulations, assurance could offer feedback on control deficiencies or help interpreting new accounting standards, transaction services could help evaluate potential acquisitions etc. etc.