(a) is the right answer as only (1) is grammatically correct. In (2), we need to replace THERE with THEIR, as we need the possessive pronoun THEIR instead of an adverb as it is being used to refer to a noun (Indian Shoppers). In (3), we need to replace the noun DANGER with the adjective DANGEROUS as it is modifying the noun VIRUS. Thus, (a) is the right answer.
If quantities of all commodities change in the same proportion then