Lois realizes that Clark is the one for her and pops the question to him FIRST, before Clark gets up the nerve to ask Lois to marry him. Maybe he hasn't even gotten that far in his reasoning. He knows he wants to spend the rest of his life with Lois, but that hasn't translated into him believing that she was ready for a proposal from him, let alone marriage. He's floored, excited, over the moon, and has the word 'yes' on the tip of his tongue.
So, does Clark tell her the truth before he accepts or afterwards? Either way, HOW does he tell her? Does this change how Lois feels towards her proposal and Clark?
RULES:
1) Lois must be serious.
2) Lois doesn't know that CK=S. Not that Clark doesn't think she does, and she really does, but hasn't told him that she knows. She must have NO IDEA.
3) The proposal comes as a surprise to Clark.