Correct option is A
The correct substitution of the highlighted words is (a)
No improvement required.
Explanation: The sentence is grammatically and contextually correct as it stands.
· "Travelling" is a
gerund functioning as the
subject, which is singular.
· “Is the best method” is a correct structure using
definite article ‘the’ before a superlative adjective
‘best’, which is also correct usage.
· “To utilise time” is a proper infinitive phrase acting as the object.
Grammatical rule used:
· Superlatives such as “best” are always preceded by “the” when referring to something specific.
· A gerund (verb+ing) can act as a singular subject.
Example:
· Reading is the best way to expand your vocabulary.