______ is known to the world, Mark Twain is a great American writer.A.ThatB.WhichC.AsD.It
______ is known to the world, Mark Twain is a great American writer.
A.That
B.Which
C.As
D.It
______ is known to the world, Mark Twain is a great American writer.
A.That
B.Which
C.As
D.It
If I had known you weren't coming, I ______ a cake.
A.would not bake
B.did not bake
C.will not have baked
D.would not have baked
He doesn't want______that he's going away.
A.to be known
B.him to be known
C.that to be known
D.it to be known
Danny didn't say anything about the matter to Mrs. Green because ______.
A.she had known it
B.the other boys would tell her
C.he didn't want to be in trouble
D.his mother didn't want him to say it
I suppose they have known about it, _______? A. am I B. am not IC. have they D. haven’t they
Danny didn't say anything about the matter to Mrs. Green because______.
A. she had known it
B. the other boys told her
C. he didn't want to be in trouble
D. his mother didn't want him to say it
______ the knowledge, he didn't know how to ask the way.
A.Knowing not
B.Having not known
C.Not knowing
D.Not to know
______he was seriously ill, I wouldn't have told him the truth.
A.If I knew
B.If I know
C.Had I known
D.Did I know
Not long age, experiments showed that birds rely on the sun to guide them during daylight hours. But what about birds that fly by night? Tests with artificial stars have proved that certain night - flying birds are able to follow the stars in their long - distance flights.
A dove (鸽子) had spent its lifetime in a cage and had never flown under a natural sky. Yet it showed an inborn ability to use the stars for guidance. The bird's cage was placed under an artificial star - filled sky. (76) The bird tried to fly in the same direction as that taken by his outdoor cousins. Any change in the position of the artificial stars caused a change in the direction of his flight.
(77) But the stars are apparently their principal means of navigation (航行) only. When the stars are hidden by clouds, they seemingly find their way by such landmarks as mountain ranges, coast lines, and river courses. But when it's too dark to see these, the doves circle helplessly, unable to find their way.
The reason why birds don't get lost on long flights ______.
A.have been known to scientists for many years
B.have only recently been discovered
C.are known by us
D.will probably remain a mystery
The first primitive cooks were 【74】 women, 【75】 preparing food and making clothing were considered women's work. 【76】 most of the great chefs in history have been men. This might have been because chefs learned 【77】 work in the kitchens of rich families 【78】 in restaurants and women didn't often take jobs outside their homes, or it might have been because kitchen equipment was so heavy and difficult to work with 【79】 only strong men could do it. In modern times, great female chefs have become known, and some of the best cook books 【80】 by women.
(71)
A.who
B.which
C.how
D.what
A. But Komfeld said scientists will not know about the applicability of the drugs in humans until a similar study is done on humans. “What’s very encouraging is that these drugs were developed to treat humans, and they are well understood, because they’ve been used for a long time, ” he said。
B. Later the scientists discovered that two related anticonvulsant drugs also lengthened the lives of the worms-in the case of one drug, by almost 50 percent. “This was a big surprise to use, Komfeld said. ”“We didn’t think anticonvulsant drugs had any particular relationship to aging. That connection was completely unexpected. ”
C. Roundworms are a poor subject for experiments, because they are not like humans, even though their molecules are similar. For example, they have no bones, nor do they show emotions, making it difficult to know how exactly human subjects would react to these drugs in large quantities. However, using the worms allows experiments to be conducted quickly, because they do not live for long。
D. “Somehow the neural activity seems to regulate the aging of all of the body the skin, musculature, and reproductive tract, ” Kornfeld said. “Somehow the nervous system coordinates the progress of all these tissues, evidently, though the life stages. But we don’t know how it does that. ”
E. The discovery may also shed light on the little-understood aging process. Since the drugs act on the neuromuscular systems of both humans and worms, the findings hint at a link between neural activity and aging。
F. Unlike vertebrates, the worms are ideal subjects for the study of aging because of their short life spans, which last only a couple of weeks in a laboratory. The worm is well known in genetics, and the worm’s genome has been sequenced。
G. Use of this drug has been permitted by law since 1998 and wider use is now expected as a result of the studies. “We can clearly link this drug with human aging, but we still need to find proof, says Kornfeld optimistically. ”
From the text we can infer a horticulturist is person engaged in ______.
A.growing plants
B.raising birds
C.cutting plants
D.studying the death cause of plants