皮皮学，免费搜题
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【简答题】
阅读下列材料，并回答问题。 甲同学在小学时学业成绩优良，对数学特别感兴趣，还在数字竞赛中得过奖，升入初中后，在第一次摸底测验中，他的成绩很不理想，在班级的排名在30几名，又受到父母的责骂，使他很有挫败感。他很想取得成绩，但又认为自己做不到，甚至连他最感兴趣的数学考试也出现不及格现象。有一次，老师还用鲜红的水笔在他的试卷上批注“字迹潦草，思维混乱，简直不是人写的”。久而久之他便对学习丧失了信心，上课不认真，拖欠作业，对考试成绩也抱无所谓的态度。 结合材料阐述教师激发学生的学习动机？
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【单选题】If two pair-elements of a kinematic pair have surface contact or its equivalent, the kinematic pair is known as a ( ).
A.
higher pair
B.
gear pair
C.
lower pair
D.
cam pair
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【单选题】If two pair-elements of a kinematic pair have surface contact or its equivalent, the kinematic pair is known as a ( ).
A.
higher pair
B.
lower pair
C.
gear pair
D.
cam pair
查看完整题目与答案
【简答题】听长对话，选择正确答案。对话读两遍。 1. What does the woman want to buy? A. A pair of jeans B. A pair of running shoes C. A pair of trousers 2. How much is the black pair? A. 25 dollars B. 45 dollars C. 50 dollars 3. W...
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【单选题】My brother has five _____ in his room. [     ]
A.
pair of shoe
B.
pairs of shoe
C.
pair of shoes
D.
pairs of shoes
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【单选题】The writer mentions______as a pair to indicate that people should have moderate feelings of guilt.
A.
eccentric people and fashionable people
B.
overanxious people and less sociable people
C.
sociable people and healthy people
D.
reserved people and radical people
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【单选题】欲配制pH=6.50的缓冲溶液,用下列何种酸最好
A.
(CH3)2AsO2H)(Ka=6.40×10-7)
B.
CICH2COOH (Ka=1.40X10-3)
C.
CH3COOH(Ka=1.76×10-5)
D.
HCOOH(Ka=1.77×10-4)
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【单选题】欲配制 pH=6.50 的缓冲溶液,最好选用 _____
A.
(CH 3 ) 2 AsO 2 H ( K a Θ =6.40×10 -7 )
B.
ClCH 2 COOH ( K a Θ =1.40×10 -3
C.
CH 3 COOH ( K a Θ =1.76×10 -5
D.
HCOOH ( K a Θ =1.77×10 -4
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【单选题】欲配制pH约为9的缓冲溶液,下列缓冲对选择哪一对最合适?()。
A.
NaH 2 PO 4 -Na 2 HPO 4 ； K a2 =6.23×10 -8
B.
HCN-NaCN ； K a =4.93×10 -10
C.
NH 3 -NH 4 Cl ； K b =1.76×10 -5
D.
HAc-NaAc ； K a =1.76×10 -5
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【单选题】汽化器式燃油系统中 , 喷油嘴出口与浮子式内燃油液面高度的关系为
A.
喷油嘴出口等于浮子室内燃油液面高度
B.
喷油嘴出口低于浮子室内燃油液面高度
C.
喷油嘴出口高于浮子室内燃油液面高度
D.
两者的高度关系不定
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【单选题】欲配制pH=6.50的缓冲溶液,下列酸最好的是:( )
A.
(CH 3 ) 2 AsO 2 H (K a =6.40×10 -7 )
B.
ClCH 2 COOH (K a =1.40×10 -3 )
C.
CH 3 COOH (K a =1.76×10 -5 )
D.
HCOOH (K a =1.77×10 -4 )
查看完整题目与答案
相关题目：
【单选题】If two pair-elements of a kinematic pair have surface contact or its equivalent, the kinematic pair is known as a ( ).
A.
higher pair
B.
gear pair
C.
lower pair
D.
cam pair
查看完整题目与答案
【单选题】If two pair-elements of a kinematic pair have surface contact or its equivalent, the kinematic pair is known as a ( ).
A.
higher pair
B.
lower pair
C.
gear pair
D.
cam pair
查看完整题目与答案
【简答题】听长对话，选择正确答案。对话读两遍。 1. What does the woman want to buy? A. A pair of jeans B. A pair of running shoes C. A pair of trousers 2. How much is the black pair? A. 25 dollars B. 45 dollars C. 50 dollars 3. W...
查看完整题目与答案
【单选题】My brother has five _____ in his room. [     ]
A.
pair of shoe
B.
pairs of shoe
C.
pair of shoes
D.
pairs of shoes
查看完整题目与答案
【单选题】The writer mentions______as a pair to indicate that people should have moderate feelings of guilt.
A.
eccentric people and fashionable people
B.
overanxious people and less sociable people
C.
sociable people and healthy people
D.
reserved people and radical people
查看完整题目与答案
【单选题】欲配制pH=6.50的缓冲溶液,用下列何种酸最好
A.
(CH3)2AsO2H)(Ka=6.40×10-7)
B.
CICH2COOH (Ka=1.40X10-3)
C.
CH3COOH(Ka=1.76×10-5)
D.
HCOOH(Ka=1.77×10-4)
查看完整题目与答案
【单选题】欲配制 pH=6.50 的缓冲溶液,最好选用 _____
A.
(CH 3 ) 2 AsO 2 H ( K a Θ =6.40×10 -7 )
B.
ClCH 2 COOH ( K a Θ =1.40×10 -3
C.
CH 3 COOH ( K a Θ =1.76×10 -5
D.
HCOOH ( K a Θ =1.77×10 -4
查看完整题目与答案
【单选题】欲配制pH约为9的缓冲溶液,下列缓冲对选择哪一对最合适?()。
A.
NaH 2 PO 4 -Na 2 HPO 4 ； K a2 =6.23×10 -8
B.
HCN-NaCN ； K a =4.93×10 -10
C.
NH 3 -NH 4 Cl ； K b =1.76×10 -5
D.
HAc-NaAc ； K a =1.76×10 -5
查看完整题目与答案
【单选题】汽化器式燃油系统中 , 喷油嘴出口与浮子式内燃油液面高度的关系为
A.
喷油嘴出口等于浮子室内燃油液面高度
B.
喷油嘴出口低于浮子室内燃油液面高度
C.
喷油嘴出口高于浮子室内燃油液面高度
D.
两者的高度关系不定
查看完整题目与答案
【单选题】欲配制pH=6.50的缓冲溶液,下列酸最好的是:( )
A.
(CH 3 ) 2 AsO 2 H (K a =6.40×10 -7 )
B.
ClCH 2 COOH (K a =1.40×10 -3 )
C.
CH 3 COOH (K a =1.76×10 -5 )
D.
HCOOH (K a =1.77×10 -4 )
查看完整题目与答案