XY型性别决定的生物,群体中的性别比例为1:1,原因是() A.雌配子数:雄配子数=

题型:单项选择题

问题:

XY型性别决定的生物,群体中的性别比例为1:1,原因是()

A.雌配子数:雄配子数=1:1

B.含X的配子数:含Y的配子数=1:1

C.含X的卵细胞数:含Y的精子数=1:1

D.含X的精子数:含Y的精子数=1:1

考点:高中生物伴性遗传伴性遗传题库
题型:单项选择题

已知一些银盐的颜色及溶解度数值如下:

化学式AgClAgBrAgIAg2SAg2CrO4
颜色白色浅黄色黄色黑色红色
溶解度/g1.5×10-47.1×10-72.1×10-71.3×10-164.3×10-2
测定水体中氯化物的含量,常用标准硝酸银法进行滴定.滴定时,应加入的指示剂是(  )

A.KBr

B.KI

C.K2S

D.K2CrO4

题型:单项选择题

年年洄游到长江中上游产卵的国家一级保护动物是[ ]

A.中华鲟

B.白鳍豚

C.桃花水母

D.娃娃鱼

题型:单项选择题

适宜行心脏移植术的是()

A.先心病,重度肺动脉高压

B.风心病,中度二尖瓣狭窄

C.扩张型心肌病,可逆性中度肺动脉高压

D.冠心病,病态窦房结综合征

E.肺心病,肺性脑病

题型:单项选择题

It's a fact that we all dream. Some dreams seem to last for hours, others only for seconds. Some of us have strange dreams, some have interesting dreams, and some of us have unpleasant dreams. Tests in the 1980s showed that these dreams occur within 90-minute cycles, each cycle made up of six stages. In the last stage people experience rapid eye movement, known as REM, and it is in this stage that dreaming takes place. Eighty percent of people who were woken during this sixth stage could easily remember their dreams. On the other hand, when during the first five stages (NREM), only seven percent could describe a dream.

However, of these same people woken during the first five stages, 74% were able to remember thinking activity, although they would not call it a dream. NerysDee, who has written about dreams in a book called "Your Dreams and What They Mean" says: "Perhaps during NREM sleep we are sorting out our outer mundane problems, but in REM sleep we are dealing with inside matters." She also makes the following statement about 90-minute cycle: It may also prove the reason why insomniacs who wake in the middle of the night find it impossible to get to sleep again for at least an hour and a half. In other words, until they have missed out one complete 90-minute sleep period.

小题1:Which of the following statements about dreams is TRUE?

A.Everyone dreams but very few can recall what they dream.

B.Some people have long dreams and others have very short ones.

C.People can only remember unpleasant dreams.

D.More than eighty percent of people can remember their dreams.小题2:According to the tests in the 1980s, dreaming takes place­­______.

A.between each 90-minute cycle

B.at any time during 90-minute cycles

C.during the first five stages of 90-minute cycles

D.in the last stage of 90-minute cycles小题3:People woken during REM sleep can______.

A.hardly remember their dreams

B.easily remember their dreams

C.only remember their dreams

D.partly remember their thinking activity小题4:"Insomniacs" are persons who______.

A.can always remember their dreams

B.have trouble getting into sleep at night

C.experience rapid eye movement

D.usually wake after each 90-minute sleep period

题型:单项选择题

除哪一项外,均可为肝脏脂肪浸润表现()

A.肝大

B.一个局灶性高回声肿块

C.血管结构减少

D.肝脏后方透声减少

E.肝脏前方回声增强

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