题干

普通小麦中有高杆抗病(TTRR)和矮杆易感病(ttrr)两个品种,控制两对相对性状的基因分别位于两对同源染色体上.实验小组利用不同的方法进行了如下三组实验,下列关于该实验的说法错误的是(    )

A:基因工程育种与C组方法比能定向改造生物性状,育种原理和A组相同

B:矮杆抗病Ⅰ中能稳定遗传的占 13

C:如果将矮杆抗病Ⅱ用于生产,还需用秋水仙素处理萌发的种子或幼苗

D:三种方法中矮杆抗病Ⅲ最难获得,因为基因突变具有不定向性

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答案(点此获取答案解析)

C

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    In the early hours of 7 September 1838, one of the worst storms in history was roaring(咆哮)along the coast of England. The lighthouse keeper1at a ship. “It will be gone in a few more minutes,” he said sadly. His daughter, Grace Darling, looking from an upstairs window, found the great ship had 2 against the rocks and broken into halves.

     “Can't we save them?” Grace asked when she saw the3people on the ship. “Isn't there any way to help them?”

“No one can take a lifeboat out in that water,” her father answered. “The waves(浪)are too large.”

    Grace had great4.She simply did not know how to give up. Filled with pity, she ran to the lifeboat quickly. Her father5. With tears running down his face, he begged his daughter not to get into the boat, 6 she would not listen. Her father could not let her go alone. He climbed in too. The two of them rowed in a great hurry. Each wave seemed 7to throw them into the sea at any time.

    Suddenly there was a terrible roar. The storm had 8the ship in two. People were holding on to each half tightly(紧紧地).They had to be saved soon.

    Grace and her father rowed faster. Soon they reached the ship and began filling the lifeboat with9. Then father and daughter brought their lifeboat safely to shore.

    As news of her brave saving action reached the public, the whole country considered her as a national hero. Grace and her father received the Silver Medal10from the British government. To this day a small statue stands above the grave(墓)of Grace Darling. People still respect the young woman who refused to give up.