The light emitted by high intensity discharge car headlights

一道AP物理题
How many different photon frequencies can be emitted if an electron is in excited state n=4 in a hydrogen atom?
A 1
B 3
C 5
D 6
E 8

英语翻译
1、A more specific version of EMI referring to emitted radio frequency electric fields-generally
in the Radio frequency (RF) bands from 3 KHz up to 3000 GHz.
2、Radiated susceptibility measures the ability of the spacecraft to operate satisfactorily
when placed in an environment that contains externally generated electric or
magnetic fields.

英语翻译
Fifty years ago,for every tonne of CO2 emitted,600kg were removed by land and ocean sinks.However,in 2006,only 550kg were removed per tonne and that amount is falling.”
Unexpected Growth In Atmospheric Carbon Dioxide

求解一道逻辑题
Nitrogen dioxide is a pollutant emitted by automobiles.Catalytic converters,devices designed to reduce nitrogen dioxide emissions,have been required in all new cars in Donia since 1993,and as a result,nitrogen dioxide emissions have been significantly reduced throughout most of the country.Yet although the proportion of new cars in Donia’s capital city has always been comparatively high,nitrogen dioxide emissions there have showed only an insignificant decline since 1993.
Which of the following,if true,most helps to explain the insignificant decline in nitrogen dioxide emissions in Donia’s capital city?
A.More of the cars in Donia’s capital city were made before 1993 than after 1993.
B.The number of new cars sold per year in Donia has declined slightly since 1993.
C.Pollutants other than nitrogen dioxide that are emitted by automobiles have also been significantly reduced in Donia since 1993
D.Many Donians who own cars made before 1993 have had catalytic converters installed in their cars.
E.Most car trips in Donia’s capital city are too short for the catalytic converter to reach its effective working temperature.
我觉得这里没有答案,但官方给的答案是E,我认为E说的是catalytic converter是否能够有效的工作,原文没说他的工作有效性啊,

一道英文化学题
Find the velocity of an electron emitted by a metal whose threshold frequency is 2.07×1014 when it is exposed to visible light of wavelength 5.24×10m.

英语成分迷惑,定语从句?
The poisonous gas emitted from vehicles undermines our lungs
The quality of our life resulting from the improvement of technology and science has already transformed
句1中的emitted,和句2中的resulting,分别是什么成分?在什么时候用主动,什么时候用被动?