题干

父本基因型为AABb,母本基因型为AaBb,其F1不可能出现的基因型是(  )

A:AABb

B:Aabb

C:AaBb

D:aabb

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答案(点此获取答案解析)

D

同类题3

阅读下列短文,从各题所给的A、B、C和D项中选出最佳选项。

    For his eleventh birthday, Lin was given a gift that would shape his life. On that day his father took him to the Children's Activity Centre and said he could choose any course that interested him. There was just one requirement: Lin would have to promise to study it for at least one year.

    To that point Lin had had many hobbies, but none kept his interest for more than a week or two. His mum once gave him a bag of stamps to encourage stamp collecting. That hobby lasted a week. Then his father got him some paints hoping that Lin's artistic side would shine through. Those paints were now under his bed, still unopened. This time Lin's parents would let him decide.

    Lin's eyes moved down the noticeboard that listed all the courses on offer. He stopped at "Photography". He liked the idea of taking beautiful pictures but the notice said that each student needed their own camera. Although Lin's family weren't poor, they weren't rich either, and a camera cost a lot of money. He continued looking.

    The next course to catch his eye was "Language Art". He didn't even know what that meant. His father explained that it taught people how to make public speeches. Lin, a shy boy, could think of nothing worse.

    Then he saw it. "Cooking" sounded like something he'd like to do. It was inexpensive and convenient, it could be done alone and it was also creative.

    Based on Lin's hobby history, his dad had doubts, but he agreed. Much to his parents' surprise, Lin kept his promise. He studied cooking at the Centre every Saturday, and practised at home, making delicious meals for his family. Everyone looked forward to birthdays, when they could eat his cakes. Lin got great satisfaction from the pleasure his food brought to others.

    The months turned to years but his hobby never changed again.

    Now Lin is an adult and runs a successful restaurant. When customers say they enjoy his meal, he still gets the same pleasure he did as a child, and remembers the special gift he received all those years ago.

同类题4

   Short and shy, Ben Saunders was the last kid in his class picked for any sports team. "Football, tennis Cricket — anything with a round ball, I was useless." he says now with a laugh. But back then he was the object of jokes in school gym classes in England’s rural Devonshire.
It was a mountain bike he received for his 15th birthday that changed him. At first the teen went biking alone in a nearby forest. Then he began to cycle along with a runner friend. Gradually, Saunders set his mind building up his body, increasing his speed, strength and endurance. At age 18, he ran his first marathon.
   The following year, he met John Ridgway, who became famous in the 1960s for rowing an open boat across the Atlantic Ocean. Saunders was hired as an instructor at Ridgway’s school of Adventure in Scotland, where he learned about the older man’s cold-water exploits (成就). Intrigued, Saunders read all he could about Arctic explorers and North Pole expeditions, then decided that this would be his future. Journeys to the Pole aren’t the usual holidays for British country boys, and many people dismissed his dream as fantasy. "John Ridgway was one of the few who didn’t say, ’You are completely crazy,’" Saunders says.
   In 2001, after becoming a skilled skier, Saunders started his first long-distance expedition toward the North Pole. He suffered frostbite, had a closer encounter (遭遇) with a polar bear and pushed his body to the limit.
   Saunders has since become the youngest person to ski alone to the North Pole, and he’s skied more of the Arctic by himself than any other Briton. His old playmates would not believe the transformation.
   This October, Saunders, 27, heads south to explore from the coast of Antarctica to the South Pole and back, an 1800-mile journey that has never been completed on skis.