why are these phrases in the parenthesis wrong?
Delagado's dilemma was (like many other) young writers. Should this one be "like that of many other" instead of what I have in the parenthesis?
Air pollution caused by industrial fumes has been studied for years, but only recently (has) the harmful effects of noise pollution become known. Should this one be "have" instead of "has?"
One challenge that writer Eleanor Wong Telemaque faced was (how preserving) her ethnic identity while becoming more accessible to readers who are accustomed to writers from other cultural backgrounds.
All states impose severe penalties on drivers who do not stop when (he or she is) involved in accidents.
You're right about the first two corrections. In the second example, the subject of the verb in the second clause is effects.
In the third example, you don't need the word how.
In the fourth example, the pronoun in the parentheses should refer to its antecedent -- drivers. What pronoun do you think should be used to refer to drivers?
they are