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问题 选择题

玉米的白花苗是变异个体，在光下也不能形成叶绿素，这种变异属于（　　）

A．有利的可遗传变异

B．不利的可遗传变异

C．有利的不遗传变异

D．不利的不遗传变异

答案

变异是指亲代间和子代个体间的差异，根据变异是否可以遗传，分为可遗传变异和不可遗传变异，遗传物质改变引起的变异属于可遗传的变异，仅由环境因素引起的变异属于不可遗传的变异．白化苗的体内不含叶绿素，无法进行光合作用，不能制造有机物，不易存活，所以属于不利变异，白化这一性状是由隐性基因控制的，所以属于可遗传变异．

故选：B

填空题

Part 4


Questions 26-45


·Read the following article and choose the best word for each space.
·For questions 26-45, mark one letter A, B, C or D on the Answer Sheet.

iPhone Left in Hot Car for Three Hours


The normally peaceful suburban town of Winnetka is still reeling following the news Monday (26) a local resident, whose name is being (27) by police pending a full investigation, left an iPhone unattended for more than three hours in a car (28) in the hot sun.
"Responding to calls from (29) . passersby, who observed the iPhone sitting in a vehicle in the parking (30) of the Westfield Shopping Center, police arrived on the (31) at approximately 4 p.m. and immediately intervened to save the device," said Winnetka police chief Douglas Blaine. "Security cameras have shown that the iPhone had been in the car— with the doors (32) and the windows rolled (33) —since 1 p.m. Due to the tragic and highly emotional (34) of this case, we cannot say any (35) at this time."
According to official police records, two officers forcibly (36) into the car at 4:07 p.m. and found the iPhone (37) face down on the dashboard. The iPhone at first showed no (38) of life, but after a tense few seconds, officers were able to wake it and get it to (39) to a series of simple touch commands. Police said that if the iPhone were left in the extreme (40) for any longer, it could have died.
The iPhone was rushed by ambulance to a nearby Apple facility for careful (41) .Miraculously, no damage to its memory, screen, or wireless capabilities was reported.
Upper-middle-class suburbanites from all over the North Shore area have reacted to the near-tragedy with an unprecedented outpouring of (42) . Hundreds of cards and letters have come streaming in, and local talk radio shows have been flooded (43) calls demanding that the iPhone’s (44) be prosecuted. Many have come forward offering to take the iPhone into their custody, and still (45) have donated free downloads, ringtones, and MP3s to the victimized object.

A．missions

B．signs

C．marks

D．symptoms
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单项选择题

行车中遇到对向来车占道行驶时怎么办？（）

A.紧靠道路中心行驶

B.主动给对方让行

C.用大灯警示对方

D.逼对方靠右行驶
查看答案