Hence, the correct answer is: Option (D) as it is not an antonym of "challenging."
Which one of the following is an antonym to the word ferocious?
Which one of the following is an antonym to the word daunt?
Which one of the following is an antonym to the word reverence?
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?