Which of the following was NOT a constraint on one

单项选择题

One of the most striking findings of a recent poll in the UK is that of the people interviewed, one in two believes that it is becoming more difficult to meet someone to start a family with.
Why are many finding it increasingly difficult to start and sustain intimate relationships Does modern life really make it harder to fall in love Or are we making it harder for ourselves
It is certainly the case today that contemporary couples benefit in different ways from relationships. Women no longer rely upon partners for economic security or status. A man doesn’t expect his spouse to be in sole charge of running his household and raising his children.
But perhaps the knowledge that we can live perfectly well without a partnership means that it takes much more to persuade people to abandon their independence.
In theory, finding a partner should be much simpler these days. Only a few generations ago, your choice of soulmate (心上人) was constrained (限制) by geography, social convention and family tradition. Although it was never explicit, many marriages were essentially arranged.
Now those barriers have been broken down. You can approach a builder or a brain surgeon in any bar in any city on any given evening. When the world is your oyster (牡蛎), you surely have a better chance of finding a pearl.
But it seems that the old conventions have been replaced by an even tighter constraint, the tyranny of choice.
The expectations of partners are inflated (提高) to an unmanageable degree, good looks, impressive salary, kind to grandmother and right socks. There is no room for error in the first impression.
We think that a relationship can be perfect. If it isn’t, it is disposable. We work to protect ourselves against future heartache and don’t put in the hard emotional labor needed to build a strong relationship. Of course, this is complicated by realities. The cost of housing and child-rearing creates pressure to have a stable income and career before a life partnership.

Which of the following was NOT a constraint on one’s choice of soulmate in the old days

A．The health condition of his or her grandmother.
B．The geographical environment.
C．The social convention.
D．The family tradition.