单选题：Text 1Today TV audiences all over the world are accustomed t

Text 1
Today TV audiences all over the world are accustomed to the sight of American astronauts in tip-top condition, withfair hair, crew-cuts, good teeth, an uncomplicated sense of humour and a severely limited non-technical vocabulary.
What marks out an astronaut from his earthbound fellow human beings is something of a difficult problem.
Should you wish to interview him, you must apply beforehand, and you must be prepared for a longish wait, even ifyour application meets with success. It is, in any case, out of the question to interview an astronaut about his familylife or personal activities, Because all the astronauts have contracts with an American magazine under conditions for-bidding any unauthorized disclosures about their private lives.
Certain obvious qualities are needed. Anyone who would be a spaceman must be in perfect health, must havepowers of concentration ( since work inside a spacecraft is exceptionally demanding) and must have considerable cour-age. Again, space-work calls for dedication. Courage and dedication are particularly essential. In the well-knowncase of the Challenger seven crew members lost their lives in space because of the faulty equipment in the shuttle.
Another must be outstanding scientific expertise. It goes without saying that they all have to have professional aero-nautical qualifications and experience.
A striking feature of the astronauts is their ages. For the younger man, in his twenties, say, space is out. Onlyone of the fifty men working for NASA in 1970 was under 30. The oldest astronaut to date is Alan Shepard,America's first man in space, who, at nearly fifty, was also the man who captained Apollo 13. The average age isthe late thirties. The crew members of Apollo 11 were all born well before the Second World War. In 1986 the Chal-lenger astronauts had an average age of 39. The range was from 35 to 46.
In a society where marital continuity is not always exhibited, the astronauts' record in this respect hits you in theeye. Of all the married men in NASA group, only two or three are divorced from their wives. Mind you, it is hardto tell whether something in the basic character of an astronaut encourages fidelity or whether the selection processdemands that a candidate should he happily married.
The NASA astronauts live in unattractive small communities dotted here and there around the base in Texas.
You would expect them to find their friends from among their professional associates, But this is not the case. Rath-er, they prefer to make friends with the normal folk in their districts. Astronauts, like everybody else, must get fedup with talking shop all the time, and whereas they are indeed an elite, their daily life outside work should be as nor-mal as possible, if only for the sake of their families.
As for the astronauts' political leanings, they seem to be towards the right. This may be due to the fact that alarge proportion of the astronauts have a military background. On the other hand, it could be just coincidence.
根据以上材料，回答题。
Details of the private life of an astronaut are hard to come by, Because they are __________. A．his own business and privacy
B．secrets as far as interviews are concerned
C．the property of an American magazine
D．the first-rate national confidential information