A. Suggest the split be 55/45 your way?

Better than option (C); but at this stage, you are an average Student in too much of a hurry to compromise.

C. Agree to their proposal?

Never. If you show people that you practise ‘split the difference’ compromises, they will simply give you bigger and bigger differences to split. As a Novice, you may not realise that.

D. Agree, but only if it is 75/25 split in your favour?

Definitely better than option (C) and more challenging for a Top Student than option (A). Possibly a better move for a Master Negotiator later on, having fully tested the amount of padding in their initial proposal.