单项选择题
双雄受精产生的合子是（ ）
A.
单倍体
B.
二倍体
C.
三倍体
D.
四倍体
E.
嵌合体
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相关考题
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未知题型
Population DensitiesThe average population density (密度) of the world is 47 persons per square milE.Continental densities range from no permanent inhabitants in Antarctica to 211 per square mile in EuropE.In the western hemisphere, population densities range from about 4 per square mile in Canada to 675 per square mile in Puerto Rico. In Europe the range is from 4 per square mile in Iceland to 831 per square mile in the Netherlands.Within countries there are wide variations of population densities. For example, in Egypt, the average is 55 persons per square mile, but 1,300 person inhabit each square mile in settled portions where the land is arable (适合耕种的).High population densities generally occur in regions of developed industrialization, such as the Netherlands, Belgium, and Great Britain, or where lands are intensively used for agriculture, as in Puerto Rico and JavA.Low average population densities are characteristic of most underdeveloped countries.Low density of population is generally associated with a relatively low percentage of cultivated lanD.This generally results from poor quality lands. It may also be due to natural obstacles to cultivation, such as deserts, mountains, or malaria-infested (疟疾横行的) jungles; to land uses other than cultivation, as pasture and forested land; to primitive methods that limit cultivation; to social obstacles.More economically advanced countries of low population density have, as a rule, large proportions of their populations living in urban areas. Their rural population densities are usually very low. Poorly developed countries of correspondingly low population density, on the other hand, often have a concentration of rural population living on arable land, which is as great as the rural concentration found in the most densely populated industrial countries.Which of the following area has the highest average population density?A.IcelanD.B.CanadA.C.Puerto Rico.D.Netherlands.
A.Within
B.
High
C.Low
D.
Low
E.This
F.
More
G.
Which
H.IcelanD.
B.CanadA.C.Puerto -
多项选择题
下面阐述正确的是()。 A、USP是传播品牌独特承诺最有效的方法,USP意味着与一个品牌的精髓所独特相关的销售主张。 B、USP广告不仅只是传播产品信息,更主要的是要激发消费者的购买行为。 C、USP学说的基本前提是,视消费者为感性思维者。 D、USP学说的语法程序是特有的许诺加理由的支持。 -
未知题型
What is the author's attitude towards one-room schools?D.Praising．
A.Critical．
B.Humorous．
C.Angry．
