试题与答案

1H-NMR中,5,7,4'-三羟基-8-甲氧基黄酮H-2'和H-6'的信号为 A.

题型:单项选择题 A型题

题目:

1H-NMR中,5,7,4'-三羟基-8-甲氧基黄酮H-2'和H-6'的信号为

A.δ7.81,二重峰
B.δ6.87,二重峰
C.δ6.68,单峰
D.δ6.20,单峰
E.δ3.82,单峰

答案:

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Floods are one of the most common disasters in the United States. However, all floods are not alike. Some floods develop slowly, sometime over a period of days. But flash floods can develop quickly, sometimes in just a few minutes and without any signs of rain.  1   It carries rocks and mud and can sweep away most things in its path. Overland flooding occurs outside a river but still can be harmful. Flooding can also occur when a dam breaks, producing effects similar to flash floods.

If a flood is likely to occur in your area, you should:

Listen to the radio for information. If there is any possibility of a flash flood, move immediately to higher ground.   2  

If you have time to prepare, you should:

Make your home safe by bringing in outdoor furniture. Move essential(必要的) items to an upper floor.   3   Do not touch any electrical equipment if you are wet or standing in water.

If you have to leave your home right away, remember these tips:

Do not walk through moving water.    4   If you have to walk in water, walk where

the water is not moving. Use a stick to check the firmness of the ground in front of you.

●    5    If flood water rises around your car, give up the car and move to higher ground

if you can do so safely. Otherwise you and the car can be quickly swept away.

The following are guidelines for the period following a flood:

Listen to news reports to learn whether the community’s water supply is safe to drink. Stay away from downed power lines, and report them to the power company

A.Do not drive into flooded areas.

B.Do not wait for instructions to move.

C.Turn off all pieces of electrical equipment.

D.Floods can cause death and loss of treasures.E. Six inches of moving water can make you fall.

F. Mud left from flood water can contain chemicals.

G .Flash floods often have a dangerous wall of roaring water.

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