Which letter in Spanish alphabet is silent ?

Which part of a car is used to drive in a certain direction?

Choose the correct answer. the phrase "por cierto" means: by certain for sure over there for now does anyone know the answer to this question?

1. el café 2. el jugo 3. las uvas 4. la leche 5. el huevo 6. el pan 7. la naranja 8. el azúcar \