Punctuation

In English grammar, relative clauses are used to provide additional information about a noun without changing the meaning of the sentence. These clauses are often introduced by relative pronouns like "who," "which," or "that." When a relative clause is non-essential or non-restrictive (meaning the sentence would still make sense without it), it should be set off by commas. This is because non-restrictive clauses add extra information that isn't crucial to identifying the noun they describe.

In the given sentence options, the clause "who lives in Mumbai" is non-restrictive as it adds additional information about "My sister" but isn't necessary to identify who "My sister" is; therefore, it needs to be enclosed with commas:

• My sister, who lives in Mumbai, is coming to visit.

This option correctly uses commas to set off the non-restrictive clause, while other options either place commas incorrectly or omit them entirely.

To choose the correctly punctuated sentence, we need to consider both grammar and punctuation rules. Let's analyze the options:

1. Its raining, we should take an umbrella.
   

   This sentence has two issues: "Its" should be "It's" (a contraction for "it is"), and there should be a semicolon instead of a comma to properly separate two independent clauses.

2. It's raining; we should take an umbrella.
   

   This sentence is correctly punctuated. "It's" is the correct contraction for "it is," and the semicolon appropriately separates the two related independent clauses.

3. Its raining; we should take an umbrella.
   

   This sentence has a contraction issue. "Its" should be "It's" to correctly mean "it is."

4. It's raining we should take an umbrella.
   

   While "It's" is correct, this sentence lacks punctuation between the two independent clauses, making it a run-on sentence. A semicolon or period is required.

Therefore, the correct sentence is: It's raining; we should take an umbrella.