Hi Mags, Llevar is a verb that has different meanings. In this question it means "to take [someone somewhere]" in which case the verb needs preposition "a". Llevar could also mean "to take [something somewhere], e.g "Llevo las cajas al almacén" - I am taking the boxes to the store room." . Here llevar doesn´t need preposition "a". So the preposition is only needed when it implies people. Thanks for your contribution.