The correct answer is E. No error.
The sentence is grammatically correct. The verb “are” agrees with the subject “health workers”. The infinitive phrase “to popularize preventive measures” is the object of the verb “are trying”. The prepositional
phrase “by the government” is the object of the preposition “by”.The sentence could be improved by adding a comma after the word “workers”. This would make it clear that the phrase “being tried their best” is a participial phrase modifying the noun “workers”.
The sentence could also be improved by adding a subject to the infinitive phrase “to popularize preventive measures”. This would make it clear who is trying to popularize preventive measures. For example, we could say “The health workers
are trying their best to popularize preventive measures by the government.”