题干

核酸是生物体内不可缺少的大分子有机物,下列关于核酸的叙述错误的是    (   )

A:核酸中所含有无素种类与磷脂中所含的元素种类一致

B:T2噬菌体的遗传物质含有4种核苷酸

C:发菜的性状都是由核区的DNA控制的

D:mRNA中含有多个密码子,而tRNA中只含有一个反密码子

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B

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      MOST recently, my world has been shaken by the death of a teacher at my school.He was Dr.Allan Woolley and he was only 52.Suddenly he took his own life, which remains a mystery.

      That morning, everyone sensed that something wasn't right.During our lessons, an announcement was made that an assembly was scheduled for morning break, which was only done in emergencies.

      Once morning break came, the entire school gathered in the main hall.As our headmaster marched out to announce the “momentous news”, it felt like the air around us trembled.Many students broke down in tears, and the reaction afterward was intensely powerful and unifying.

    The headmaster said that students were allowed to miss lessons and have a free period to collect themselves if they found the news too distressing.Many students went outside and shared memories of Dr.Woolley to control themselves.

     Dr.Woolley taught me chemistry two years ago, but up until his death he still taught many of my close friends.Many of my friends were so shocked that they still couldn't believe the person that they had owed some homework to was now dead.

      It was heart­warming to spend time with teachers that morning and get to know more about them.Despite the time of sadness, I feel that every cloud has a silver lining.Although Dr.Woolley's death is something nobody wanted to see, we must move on.

Notes:

①assembly n.集会 ②schedule vt.安排 ③momentous adj.重大的 ④unifying adj.统一的 ⑤distressing adj.悲伤的