"Those with a large social circle are actually less satisfied with their lives than those

with a smaller group of friends who are close to them." This finding appears in a report released last week, which is a part of the product of a 1-year social research program. More than 1,000 persons are interviewed about their attitude and feeling for their friends. And those interviewed are diversified, from the perspective of gender, age, and occupation as well as marital statues.

"Of course, we can not imagine a life without any friend", said Jeff, one of the researchers from the research program, "but when it comes to friends, it is definitely not a matter of the more, the better". He also pointed out that with our growing up, the life situation in front of us will become complicated, and some of the friends, especially those we made while doing business, will turn out to be more like a burden than a support, which may sound surprising to those who haven't put too much thought into this issue.

If you are really busy, and some friendships seem to have nothing to offer you at the moment, maybe you can consider cooling the relationship for a while. When these friends invite you to a social gathering and you do not have the time to do so, decline such invitations politely. When they call you for a casual chat, and you are really having your hands full at that particular time, try to control that call to a time period acceptable for you.

We use the term "to cool some friendship", because we are by no means indicating a utilitarianism attitude towards friendship--an attitude that the value of a friend would be determined by whether or not he/she is useful for us. We agree with the general belief that friendship should be kept as something pure and lasting. What we are suggesting here is how to find a balance between the quality and quantity of friends.

So, for those friendships we cooled off for a while, if you don't want to cut them off completely, you can organize some gatherings with a few such friends on a quarterly or even yearly basis. By doing so, you can keep several friendships going on at once.

Which of the following factor is NOT mentioned when discussing the persons interviewed in the research？

A．What kind of job they are doing.

B．How old they are.

C．How much money they earn per year.

D．Whether they are married or not.