Question 1
(1).The bittersweet flavor of youth–its trials, its joys, its adventures, its challenges–ARE not soon forgotten.
(2).The bittersweet flavor of youth–its trials, its joys, its adventures, its challenges–IS not soon forgotten.
and
Question 2
(1).One of the ablest scientists who HAS attacked this problem.
(2).One of the ablest scientists who HAVE attacked this problem.
which one is the right one? I think the second in the first question is right, and the first in the second is right,but the didn’t provide me the answers. So…
‘Is not soon forgotten’ is right. In the second sentence you have to decide which noun ‘who’ refers to and that has to be ‘scientists’. As this is plural, you need to say ‘have’. The sentence would make better sense if it was completed as: One of the ablest scientists who HAVE attacked this problem, is Professor Knowall.
You have to use ‘is’ not ‘are’ there because Professor Knowall’ is singular.
Consider the same meaning with a different structure: Professor Knowall is one of the ablest scientists.
Because there, ‘have’ refers to ‘the ablest scientists’ (plural).
Reworded:
Professor Knowall is one of the ablest scientists who have attacked this problem.
This isn’t so eloquent a sentence (in fact it’s poorly written), but perhaps it would be easier for you to see the connection:
Of all the able scientists (plural) who have (plural form) attacked this problem, Professor Knowall (singular) is one who has (singular form) tried.
It just sounds clunky, long-winded and clumsy. It is not a good example of writing or speaking, but it serves a purpose here.
Under normal circumstances, there are so many ways of writing this idea which sound more natural:
Compare
Of all the able scientists who have attacked this problem, Professor Knowall is one who has tried.
with
Among the able scientists who have attacked this problem, is Professor Knowall.
Professor Knowall is among the able scientists who have attacked this problem.
One of the ablest scientists who have attacked this problem, is Professor Knowall.