问题
单项选择题
关于牙齿的发育，下列说法不正确的是（）
A.牙齿生长是骨成熟的一个粗指标
B.人有两副牙齿，即乳牙和恒牙
C.6岁左右，儿童开始换牙
D.儿童长出的第一颗恒牙是切牙
E.一般12岁长出第二磨牙
答案
参考答案：D
解析：自6岁左右，儿童开始换牙。在全副乳牙之后长出第一颗恒牙（第一磨牙），然后基本按从前至后的顺序逐个替换同位乳牙。
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关于牙齿的发育，下列说法不正确的是（）
A.牙齿生长是骨成熟的一个粗指标
B.人有两副牙齿，即乳牙和恒牙
C.6岁左右，儿童开始换牙
D.儿童长出的第一颗恒牙是切牙
E.一般12岁长出第二磨牙
参考答案：D
解析：自6岁左右，儿童开始换牙。在全副乳牙之后长出第一颗恒牙（第一磨牙），然后基本按从前至后的顺序逐个替换同位乳牙。
It was Christmas Eve. It was very cold. A 1 girl was selling flowers on the street. Her parents were ill, 2 she had to get money 3 food. She felt cold and hungry. She 4 in front of a beautiful house. The girl knocked at the door and a man came out. She asked him if he 5 some flowers. The man said he didn’t want any. She left the house and felt tired. She sat down at the foot of 6 tall wall. She looked at the flowers. The flowers smelled very nice. She suddenly had a strange feeling. She felt she was becoming light, and slowly she began to fly into the sky. She flew higher and higher and at last she found 7 above the clouds. A group of people were coming to meet her. At the head of them was her granny. Granny welcomed her and asked her 8 she didn’t stay at home. The girl told her that she 9 to sell flowers to get money because her parents were badly ill. Granny told her not to worry and gave her 10 of beautiful clothes and delicious food. The girl laughed happily.
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