The word "optimistic" means having a hopeful and positive outlook on a situation, which makes "hopeful" (Option D) the correct synonym.
Thus, the correct synonym for "optimistic" is "hopeful."
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?