Select the option that will improve the highlighted part of the given sentence. In case no improvement is needed, select 'No improvement required'.
Siliguri has joined the nation to celebrate the golden jubilee of the first conquest of Mount Everest by an Indian.

Correct option is C

The correct substitution of the highlighted words is (c) No improvement required.
Explanation:
The sentence is in present perfect tense and grammatically correct. “Has joined” shows a recent completed action with present relevance. “To celebrate” correctly shows purpose. The structure is logical and needs no change.
Grammatical rule used:
Present perfect tense: has/have + past participle
Purpose clause: to + base verb
Example: She has joined the club to learn dance.
Incorrect options:
· (a) changes the sentence structure unnecessarily.
· (b) “celebratory nation” is not contextually appropriate.
· (d) ungrammatical — "joining the nation celebrate" is incorrect.