Replace the underlined words with a suitable option:
When I was a student - I carried a packed lunch to school every day.
A) student; I
B) student I
C) student, I
D) NO CHANGE

Hint: A clause is a group of words, which has a Subject and Predicate of its own, makes complete sense and forms part of a larger sentence. There are three kinds of clauses – The Noun Clause, The Adjective Clause and The Adverb Clause.

Complete answer:
Clauses are generally two types - independent clauses or main clauses and dependent clauses or subordinate clauses. The given sentence is formed by two parts - an adverbial clause and the main clause. And the adverbial clause begins with a subordinating conjunction.

Now let us analyze the given options:
Option A) student; I: The above option is incorrect as the given sentence is formed by an adverbial clause and the main clause, in order to separate these two clauses, a comma should be used. But, in this option, a semicolon is placed between them which can only be used with independent clauses.

Option B) student I: The above option is incorrect as the given sentence is formed by an adverbial clause and the main clause, in order to separate these two clauses, a comma should be used. But, in this option, nothing is placed between them which makes the sentence not meaningful.

Option C) student, I: The above option is correct as the given sentence is formed by an adverbial clause and the main clause, in order to separate these two clauses, a comma must be placed between them.

Option D) NO CHANGE: The above option is incorrect as the given sentence is formed by an adverbial clause and the main clause, in order to separate these two clauses, a comma should be used. But, in this option, the en dash is placed between them which can only be used between words to represent conflict, relation and direction and its use are unnecessary.

Therefore the correct answer is option ‘C’.

Note: The main clause or an independent clause must contain a subject and a verb and thus, together expresses a complete thought. Subordinate clauses always begin with subordinating conjunctions, which are words that join dependent clauses to independent clauses, such as for, as, since, therefore, hence, consequently, though, due to, provided that, because, unless, once, while, when, whenever, where, wherever, before, and after. Sometimes, they also begin with relative pronouns such as that, which, who, whom, whichever, whoever, whomever, and whose.