The correct option is:

Remember that to answer these types of questions we must know the basic verbs.
The exercise gives us a choice of four options, that is, four verbs.
- Prueba (Probar) ⇝ To taste
- Compra (Comprar) ⇝ To buy
- Vende (Vender) ⇝ To sell
- Viene (Venir) ⇝ To come
In the sentence he tells us that the girl is tasting the tea we choose "prueba".