题干

下图为某植物在夏季晴天一昼夜内CO2吸收量的变化情况,以下判断正确的有几项(   )

(1)该植物进行光合作用的时间区段是bg段
(2)该植物在a和h时刻只进行呼吸作用,不进行光合作用
(3)影响bc段光合速率的外界因素只有光照强度
(4)ce段与fg段光合速率下降的原因完全相同
(5)若c、f时刻的光合速率相等,则该植物呼吸速率为c时刻大于f时刻
(6)该植物处于生长时期

A:四项

B:一项

C:三项

D:二项

上一题 下一题 0.0难度 选择题 更新时间:2017-02-17 03:58:17

答案(点此获取答案解析)

D

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    Are you nervous about climbing because you think it's too dangerous?Do you feel you're not fit enough to climb?Do you know how to start climbing?

    Let's consider the idea that climbing is dangerous.Being afraid is natural,but if you use suitable ropes and other climbing equipments you will feel completely safe.Climbers are usually very careful because they know what they are doing is dangerous.Accidents may happen,but when they do,they tend to attract a lot of publicity.As a result, people think there are many more accidents than there are in reality.

    You cannot expect to start climbing straight away.Climbing is a challenge and challenges take time.It is necessary first of all that you achieve a good level of fitness.Begin as soon as you become interested in climbing—go to the gym,go swimming,take up jogging and continue to do so throughout your training period.

    Discover as much as you can about climbing.Visit the library and find books especially for beginners or buy climbing magazines and look for articles which describe your situation.Look up information on the Internet.Find out about equipment,methods and places to go.

    Next,take a course on a climbing wall.There are plenty of climbing walls all over the country which have trained and qualified people as instructors.Call your local leisure centre to find out if there is one in your area.These training sessions are a quick way to get experience and you are likely to meet other beginners.After this,you can do an outside course or join a club where you can meet climbers of all abilities and eventually join in group-climbing events.

    At first you may not understand the importance of a good training period,but after you have completed your first climb and you are standing safely at the top of a rock feeling thrilled,then you will know it was the right thing to do.