Nerve and nerve transmission PLEASE HELP!

so the question is: Explain why another action potential cannot be generated during repolarisation

but i don't really understand the whole resting potential (how it is maintained), depolarisation, repolarisation and hyperpolarisation. Any help or explanation would be very much appreciated!

This is quite a broad question, given you would need to have an understanding of those processes in order to answer the question. I would recommend reading some guides or texts books on the topic in order to understand the mechanisms.

If you're more of a visual learner, this video explains the topic really well (particularly the refractory period for your question): https://www.youtube.com/watch?v=Gsf9IB-wQdU

Hope this helps