题目内容
（请给出正确答案）
Advection fog may be formed by cold air passing over a ______.
A.colder sea surface
B.warmer sea surface
C.dry coastal plains
D.high mountain or plateau
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更多“Advection fog may be formed by…”相关的问题
More than 60,000 people have purchased the PTKs since they first become available without prescriptions last years, according to Doug Fog, chief operating officer of Identigene, which makes the over-the-counter kits. More than two dozen companies sell DNA tests Directly to the public , ranging in price from a few hundred dollars to more than $2500.
Among the most popular : paternity and kinship testing , which adopted children can use to find their biological relatives and latest rage a many passionate genealogists-and supports businesses that offer to search for a family’s geographic roots .
Most tests require collecting cells by webbing saliva in the mouth and sending it to the 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 by people claiming they are doing ancestry testing,” says Trey Duster, a New York University sociologist. He notes that each individual has many ancestors-numbering in the hundreds just a few centuries back. Yet most ancestry testing only considers a single lineage, either the Y chromosome inherited through men in a father’s line or mitochondrial DNA, which a passed down only from mothers. This DNA can reveal genetic information about only one or two ancestors, even though, for example, just three generations back 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 reference collections to which a sample is compared. Databases used by some companies don’t rely on data collected systematically but rather lump together information from different research projects. This means that a DNA database may differ depending on the company that processes the results. In addition, the computer programs a company uses to estimate relationships may be patented and not subject to peer review or outside evaluation.
26.In paragraphs 1 and 2 , the text shows PTK’s ___________.
[A]easy availability
[B]flexibility in pricing
[C] successful promotion
[D] popularity with households
The search was ______ when the fog got thicker.
A．called off
B．called on
C．called in
D．called for
______ the fog, we should have reached our destination.
A．Because of
B．In spite of
C．In case of
D．But for
A.Because of
B.In spite of
C.But for
A.dense
B.compressed
C.concentrated
D.closed
A.moderate speed
B.safe speed
C.half speed
D.bare steerageway
