The correct option is B a little
In the above sentence, the noun is uncountable so "few" is a wrong option as it is used for only countable nouns. On the other hand little and "a little" are used when the noun is uncountable. soup is a liquid substance which is uncountable. Thus we would be using either "little" or "a little". Now, let us understand the difference between "little" and "a little". "Little" is used when a very small quantity is considered whereas "a little" is used when a quantity greater than "little" is used. In other words, "a little" also means "some", "not many". In this case specifically the amount specified is some. So, the answer is B, "a little"