Answer:
Reciclas botellas de plástico.
Step-by-step explanation:
The only sentence that is not a mandate is 'Reciclas botellas de plástico', which means 'you recycle plastic bottles'. It is an affirmation.
The other sentences are mandates because the first one ('No te caigas de la silla') indicates something that you do not have to do, and the other one ('Haz cinco ejercicios en el libro'), is an order.