Answer:
B). My sister and I stayed in shady corners and in front of old plastic fans.(proper noun replaced by a common noun)
D). Sid, my sister, and I stayed in shady corners and in front of old plastic fans.(Proper noun replacing common noun)
Step-by-step explanation:
A proper noun is described as the noun that denotes a particular person, organization, place, animal, etc. while a common noun denotes a generic name of any member of a class, category, etc. The above sentence replaces the proper noun with a common noun(general name 'my sister' instead of being particular 'Sid') and a common noun with a proper noun(by naming the specific sister 'Sid' who is being talked about in the sentence). Thus, options B and D are the correct answers.