
例:h﹣(u)﹣ā→huā
|
x﹣üě→ |
c﹣﹣ò→cuò |
m﹣→miè |
|
b﹣﹣àn→biàn |
n﹣ǚ→ |
﹣﹣→jiang |
(其中
为自然对数的底数)图象的大致形状是( )
B .
C .
D .
,上衣和裤子各多少钱?
时,电源有最大的输出功率
B . 当
时,电源的效率
C . 电源的输出功率P随外电阻R的增大而增大
D . 电源的效率
随外电阻R的增大而增大

Comfort Zone is a state of mind where there is the least stress (压力). However, stepping into the learning zone can help to bring out the best in us. Here are the reasons.
▲Challenging yourself can help you do at your best.
Stepping outside one's comfort zone is important to personal development. How can we expect to make ourselves better if we only stick to habit and routine (日常)? We should try something we might not succeed at.
▲Taking risks is what helps us grow.
As children, we're natural risk takers. But as we get older and learn to fear failure (失败), we start trying fewer new things. We pay a heavy price for our fear of failure. There is no learning without some difficulty.
▲Facing new challenges can help us age better.
Our comfort zones seem to become smaller as we get older一but if we can keep expanding them, we'll open ourselves up to a greater world as we age. As we step into the learning zone, we will get more comfortable with the skills gradually and we'll start to move into the comfort zone. A study found that learning new life skills can help our brain stay sharp (敏锐的) as we get older.
However, don't push yourself too far. Have you heard of "Yerkes-Dodson Law"? It means performance increases as stress grows, but only up to a point. If the level of stress becomes too high, performance will go down. When stress becomes too great for us to deal with, we enter the danger zone.
B .
C .
D .
实验1 |
| 实验现象 |
液面上方产生白色絮状沉淀,迅速变为灰绿色,振荡,试管壁上有红褐色沉淀生成. |
①甲同学推测灰绿色物质为Fe(OH)2和Fe(OH)3混合物.查阅资料后根据调色原理认为白色和红褐色的调和色不可能是灰绿色,并设计实验证实灰绿色物质中不含有Fe(OH)3 , 方案是.
②乙同学查阅文献:Fe(OH)2在大量SO42﹣存在的情况下形成Fe6(SO4)2(OH)4O3(一种氧基碱式复盐).并设计对比实验证实该假设:向试管中加入,再往试管中加入,振荡,现象与实验1相同,结论是该假设不成立.
③乙同学继续查阅文献:Fe(OH)2沉淀具有较强的吸附性能,灰绿色可能是由Fe(OH)2表面吸附Fe2+引起.推测所用的硫酸亚铁溶液的浓度应越小越好;氢氧化钠溶液浓度应越大越好.设计了如下实验方案:
试管中10mL NaOH溶液 | 滴加 FeSO4溶液 | 实验现象 | |
实验2 | 6mol/L NaOH溶液 | 0.2mol/L FeSO4溶液 | 产生悬浮于液面的白色沉淀(带有少量灰绿色),沉淀下沉后,大部分灰绿色变为白色沉淀 |
实验3 | 6mol/L NaOH溶液 | 0.1mol/L FeSO4溶液 | 产生悬浮于液面的白色沉淀(带有极少量灰绿色),沉淀下沉后,底部都为白色沉淀 |
该实验得出的结论是,能说明灰绿色是由Fe(OH)2表面吸附Fe2+引起的证据是.丙同学认为该实验方案不足以证明灰绿色是由Fe(OH)2表面吸附Fe2+引起的,还需补充的实验是,证明该假设成立.
①中国向疫情严重的国家捐赠医疗物资
②武汉遭遇严重疫情,祖国各地主动伸出援助之手驰援武汉
③同学们陆续复课返校,好开心
④“澳洲跑步女”无视当地的隔离规定,坚持外出跑步
8+414 7+44+7
135+7 19-211+3