下列四种关于芽的分类中，正确的是______。 A．芽有顶芽、定芽_爱下问搜题

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问题单项选择题

下列四种关于芽的分类中，正确的是______。

A．芽有顶芽、定芽和不定芽三种
B．芽有叶芽、花芽和混合芽三种
C．芽有活动芽、裸芽和被芽之分
D．芽有休眠芽、活动芽和潜伏芽之分

答案

参考答案：B

解析：芽的分类包括按结构分为叶芽、花芽、混合芽；按生长位置分为定芽(顶芽、腋芽)、不定芽；按芽外有无牙鳞分为鳞芽、裸芽；按生长形态和形成季节分为休眠芽、活动芽。故B项正确。

阅读理解

I remember my first Christmas party with Grandma．I remember the day when my big sister dropped the bomb: “There is no Santa Claus,” she laughed．“Even dummies know that!”
　　I fled to Grandma because I knew she always told me 21 ．After I told her everything, she said “No Santa Claus? Don’t believe it. Now, 22 your coat, and let’s go.”
　　“Go? Go where?” I asked．
　　“Where” 23 to be the General Store．As we walked through its doors, Grandma 24 me ten dollars．That was a lot in those days．“Take this money and buy something for 25 needs it．I’ll wait for you in the car．”
　　The store seemed big and 26 , full of people hurrying to finish their Christmas shopping．For a few moments I just stood there, 27 , holding that bill, wondering what to buy, and who on earth to buy it for．
　　Suddenly I thought of Bobbie who sat right behind me．I remembered he didn’t have a coat．I fingered the bill with growing 28 ．I would buy Bobbie a coat．
　　“Is this a Christmas present for someone?” the lady behind the 29 asked me kindly, as I laid my ten dollars down
　　“Yes,” I replied shyly．“It’s…for Bobbie.”
　　The nice lady smiled at me．I didn’t get any 30 , but she put the coat in a bag and wished me a Merry Christmas．
　　That evening, Grandma helped me 31 the coat and wrote, “To Bobby, From Santa Claus” on it．Then she 32 me over to Bobbie’s house．
　　Grandma parked down the street from Bobbie’s house, and she and I crept 33 and hid in the 34 ．Then Grandma gave me a sign．“All right, Santa Claus, get going．”
　　I took a deep 35 , dashed for his front door, threw the present down, pounded his doorbell and flew back to the safety．Together we 36 breathlessly in the darkness for the front door to open．Finally it 37 , and there stood Bobbie．
Forty years haven’t dimmed the thrill of those 38 spent shivering, beside my grandma, in Bobbie’s bushes． 39 , I realized: Santa was alive and well, and we were 40 his team．

B．many things

C．someone who

B．disappointment

D．encouragement

D．noiselessly

单项选择题

体内钙的主要存在形式是（）。

A.碳酸钙

B.磷酸钙

C.羟磷灰石

D.羟钙灰石

E.混溶钙池