The appropriate option to complete the sentence is: few people can speak a foreign language really fluently.

1. Little: "Little" is used for uncountable nouns to indicate a small amount or quantity. However, in this context, we are talking about people, which is a countable noun.

2. A little: Similar to "little," "a little" is used for uncountable nouns. It indicates a small amount. Again, it doesn't fit well with the context of people.

3. Few: "Few" is used for countable nouns and means a small number of people.

4. The few: "The few" refers to a specific small number of people, often implying that there are not many but emphasizing those that exist. However, in this sentence, we are making a general statement about the ability of some people to speak a foreign language fluently.