Answer:
1. If it rains, we won't go to the beach.
2. Ms. Smith, who lives next door, came to borrow some sugar.
3. You must be really proud of your mother, aren't you?
Explanation:
1. The use of the comma is obligatory after introductory clauses or phrases. All the markers for the introductory clauses are always followed by a comma (if, since, while, after, because, etc.).
2. The use of the comma to offset a clause in the middle of a complete sentence is mandatory, as those clauses provide additional information to the complete sentence.
3. The use of comma to offset a clause at the end of a sentence is mandatory, in order to separate contrasting elements or to denote a pause during the speech.
A is the incorrect option
For example, the author praises her for her willingness to accept and showcase her Mexican culture. He also notes her unique character of pursuing her passion and gifts; that of painting, something most women in her time were not into.
