The indefinite articles "a" and "an" are used based on the sound that follows them:
The correct sentence should be:
"On Wednesday, I bought a pair of shoes and an umbrella from the department store located on Sixth Avenue."
Thus, the correct answer is Option B ("a-an").
Arun’s present age in years is 40% of Barun’s. In another few years, Arun’s age will be half of Barun’s. By what percentage will Barun’s age increase during this period?