Correct Answer :
B. Covert : Stealthy
The given words in question are synonyms, as both can refer to conducted with or marked by hidden aims or methods and the words given in option (b) are also synonyms as both can refer to secret or something thats not done openly. Option (a) is wrong, because it doesnt depict the same relationship: overt can refer to observable or something thats not secret or hidden whereas, furtive refers to something that is done quietly or cautiously.
Option (c) is wrong: open is the opposite of close; these are not similar words. Option (d) is wrong, because news and rumour are again, antonyms.