Fairly and rather
A. Both can mean ‘moderately’, but fairly is chiefly used with ‘favorable adjectives and adverbs (bravely, good, nice, well etc.), while rather is chiefly used in this sense before ‘unfavorable’ adjectives and adverbs (bad, stupidly, ugly etc.): Tom is fairly clever, but Peter is rather stupid. I walk fairly fast but Ann walks rather slowly. [...]
