Questions are based on the following passage. It is a wise father that knows his own chi

Questions are based on the following passage.

It is a wise father that knows his own child， but today a man can boost his paternal （fatherly）wisdom —— or at least confirm that he"s the kid"s dad. All he needs to do is shell out $30 forpaternity testing kit （PTK） at his local drugstore —— and another $120 to get the results.

More than 60，000 people have purchased the PTKs since they first become availablewithout prescriptions last years， according to Doug Fogg， chief operating officer ofIdentigene， which makes the over-the-counter kits. More than two dozen companies sell DNAtests directly to the public， ranging in price from a few hundred dollars to more than $2，500.

Among the most popular: paternity and kinship testing， which adopted children can useto find their biological relatives and families can use to track down kids put up for adoption，DNA testing is also the latest rage among passionate genealogists —— and supports businessesthat offer to search for a family"s geographic roots.

Most tests require collecting cells by webbing saliva （唾液） in the mouth and sending it tothe company for testing. All tests require a potential candidate with whom to compare DNA.

But some observers are skeptical. "There is a kind of false precision being hawked bypeople claiming they are doing ancestry testing，" says Trey Duster， a New York Universitysociologist. He notes that each individual has many ancestors —— numbering in the hundredsjust a few centuries back. Yet most ancestry testing only considers a single lineage （世系），either the Y chromosome （染色体） inherited through men in a father"s line or mitochondrial（线粒体） DNA， which is passed down only from mothers. This DNA can reveal geneticinformation about only one or two ancestors， even though， for example， just three generationsback people also have six other great-grandparents or， four generations back，14 other great-great-grandparents.

Critics also argue that commercial genetic testing is only as good as the referencecollections to which a sample is compared. Databases used by some companies don"t relyon data collected systematically but rather lump together information from different researchprojects. This means that a DNA database may have a lot of data from some regions and notothers， so a person"s test results may differ depending on the company that processes theresults.

According to the passage， what is PTK used to？ 查看材料

A.To locate one"s birth place.

B.To promote genetic research.

C.To find out if one is the father of a child.

D.To help improve one"s intelligence.