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【单选题】
This action affects the environment as a whole . For example , a lot of carbon dioxide in the air comes from burning the rainforests . People obviously have a need for the resources we gain from cutting trees but we will suffer much more than we will benefit. There are two main reasons for this . Firstly , when people cut down trees , generally they can only use the land for a year or two . Secondly ,...A.
We will lose much more than we can gain ．
B.
Humans have begun destroying rainforests ．
C.
People have a strong desire for resources ．
D.
Much carbon dioxide comes from burning rainforests ．
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【单选题】根据三级预防的原则劳动卫生及职业病工作的第二级预防应进行以下工作
A.
劳动者的健康检查
B.
早期识别、判断职业性病损的人群
C.
建立健康档案，定期随访监护
D.
对可疑及确诊病人进行针对病因的治疗
E.
对受损者做劳动能力鉴定
【简答题】可压缩性流体在管道内稳定流动的连续性方程为______。 (A)u 1 A 1 =u 2 A 2 (B)u 1 A 2 =u 2 A 1 (C)u 1 A 1 /ρ 2 =u 2 A 2 /ρ 1 (D)u 1 A 1 /ρ 1 =u 2 A 2 /ρ 2
【单选题】可压缩性流体在管道内稳定流动的连续性方程式为( )
A.
u 1 A 1 =u 2 A 2
B.
u 1 A 2 =u 2 A 1
C.
u 1 A 1 /ρ 1 =u 2 A 2 /ρ 2
D.
u 1 A 1 ρ 1 =u 2 A 2 ρ 2
【单选题】可压缩性流体在管道内稳定流动的连续性方程式为( )
A.
u1 Ａ 1/ ρ 1=u2 Ａ 2/ ρ 2
B.
u1 Ａ 1=u2 Ａ 2
C.
u1 Ａ 2=u2 Ａ 1
D.
u1 Ａ 1/ ρ 2=u2 Ａ 2/ ρ 1
【单选题】可压缩性流体在管道内稳定流动的连续性方程式为( )
A.
u1A1/ρ1=u2A2/ρ2
B.
u1A1=u2A2
C.
u1A2=u2A1
D.
u1A1/ρ2=u2A2/ρ1
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