rkav wrote:Often visible as smog, ozone is formed in the atmosphere from hydrocarbons and nitrogen oxides, two major pollutants emitted by automobiles, react with sunlight.

a) same.
b) ozone is formed in the atmosphere when
c) ozone is formed in the atmosphere, and when
d) ozone, formed in the atmosphere when
e) ozone, formed in the atmosphere from


Can someone explain why "when" is used here. I thought "when" can only be used to refer t a specif time/period?

Thanks

Your understanding of when is right.

I think, over here the selection between "when" and "from" depend more on logical sense than grammatical sense.

The mere presence of hydrogen and nitrogen oxides is not sufficient to form ozone. It require one more element, Sunlight. So when Nitrogen oxides and hydrogen comes in proximity to each other in presence of sunlight, ozone is formed.

If you use "from" in-place of "when" you mean that the hydrogen and nitrogen oxide is sufficient enough.

Hope it helps.

rkav wrote:Often visible as smog, ozone is formed in the atmosphere from hydrocarbons and nitrogen oxides, two major pollutants emitted by automobiles, react with sunlight.

a) same.
b) ozone is formed in the atmosphere when
c) ozone is formed in the atmosphere, and when
d) ozone, formed in the atmosphere when
e) ozone, formed in the atmosphere from


Can someone explain why "when" is used here. I thought "when" can only be used to refer t a specif time/period?

Thanks

Hemant,
'When' can also be used to refer to a particular event. For e.g.
He woke up when the alarm went off.
In this question, the intended meaning is 'When X and Y react, Z is formed'.

a) ozone is formed in the atmosphere from - This option will be correct if we don't have 'react with sunlight'
b) ozone is formed in the atmosphere when - Ozone is not jus formed from X & Y always. It is formed at the moment when X & Y react with sunlight. This is the reason why 'from' is wrong and 'when' is correct.
c) ozone is formed in the atmosphere, and when - 'and' here is wrong coz it means that the formation and reaction are independent events. It is not correct, it is coz of the reaction we get ozone.
d) ozone, formed in the atmosphere when - Lacks the verb 'is'
e) ozone, formed in the atmosphere from - Same reason as A & D

Hence B !

Gowri@CrackVerbal wrote:

rkav wrote:Often visible as smog, ozone is formed in the atmosphere from hydrocarbons and nitrogen oxides, two major pollutants emitted by automobiles, react with sunlight.

a) same.
b) ozone is formed in the atmosphere when
c) ozone is formed in the atmosphere, and when
d) ozone, formed in the atmosphere when
e) ozone, formed in the atmosphere from


Can someone explain why "when" is used here. I thought "when" can only be used to refer t a specif time/period?

Thanks

Hemant,
'When' can also be used to refer to a particular event. For e.g.
He woke up when the alarm went off.
In this question, the intended meaning is 'When X and Y react, Z is formed'.

It is same as referring to particular time or event. You and the rkav both have same understanding, just words difference.