“Fewer” / “less”
Answer A is better.
“Fewer” is used with countable nouns: Fewer students are learning foreign languages these days.
“Less” is used with uncountable nouns: Schools are spending less time and less money on foreign languages. In spoken English, many people use “less” for countable nouns, too: Less people speak foreign languages.
Our tip: If you are writing in an academic or professional context, you will make a far better impression if you know the difference between “less” and “fewer”.