Which line from the passage causes a shift in Ursula's perspective on marrying Mark?

A.
When I had read it I cast myself on the bed and wept out all the tears I had refused to let myself shed during my weeks of exile.
B.
"Well, no, I wouldn't advise you to," said Aunt Philippa reflectively. "It's a kind of low-down thing to do, though there's been a terrible lot of romantic nonsense talked and writ about eloping.”
C.
If I would not, he would understand that I had ceased to love him and that all was over between us.
D.
You're too young to be married, but if you let him go off to South Africa he'll slip through your fingers for sure, and I s'pose you're like some of the rest of us—nobody'll do you but the one.