The right answer is A. Cuando Carlos y Sofìa estuvieron en Costa Rica, viajaron en tren varias veces.
This means: <span>When Carlos and Sofía were in Costa Rica, they traveled by train several times. </span> The keywords are "estuvieron" (were), that<span> is the past of "estar". And the "viajaron" (traveled), that is the past of "viajar" (Travel). </span><span>In the other sentences, the past is not well conjugated. </span> <span /><span>I hope this information can help you.</span>
