Ответ:

  1. Many people talk but few have something to say.
  2. You need a few potatoes to make some pancakes.
  3. A little porridge is enough for my breakfast.
  4. This lemon drink is sour. Put a few lumps of sugar in it.

Обоснование: few / a few используются с исчисляемыми существительными во множественном числе, а little / a little — с неисчисляемыми.