资料题：According o the passage, when do most American men propose（　）。

What better occasion than Valentine's day to ask for your sweetheart's hand? In America,the answer is almost any other.Most love-struck American men are unaware of the perils of proposal.Many will this weekend surprise girlfriends with a diamond engagement ring.Suitors (求偶者) would do well to consider what might happen to that expensive rock if the engagement is broken off before the wedding day.Etiquette and common sense dictate that the ring should be returned to the man.In many states, that is what the law requires too.But not all.Brian Bix, a law professor at Quinnipiac College in Connecticut, points out that in some parts of America it matters who is responsible for the break-up.In his state, if the man is to blame, legal precedent suggests that the woman keeps the ring.Things are not so clear in neighbouring New York.When the ring is given might matter too, for some states could let the fiance keep the ring if she can convince a count that it was an"unconditional" gift, rather than one given for possible marriage.Legal scholars say this is a very tricky point.But one thing is clear.A woman could strengthen the argument that the ring was given unconditionally if she had received it on a traditional gift-giving occasion- such as Valentine's day.Luckily for romance, De Beers brought to the market an undisputedly eternal option: the Millennium diamond, which comes with a serial number and an appropriately epochal(新纪元的)logo(标识语)etched (蚀刻) into the stone by lasers.Officials a the diamond cartel(企业联合)are confident that the limited edition of 20,000 gems will go fast.No doubt many men will rush to buy these diamonds, which De Beers vows not to issue again until 3000.How could any follow fail to win his girl's heart with such a"once-in-a-millennium"token (信物) Just to be safe, though, better not give it on her birthday.