C. Because you are using the 3rd person singular of the verb in the present tense
On his visit to the Galapagos Islands, Charles Darwin discovered several species of finches that varied from island to island, which helped him to develop his theory of natural selection
Do you have a list of word options?
El banquero deposito nuestro dinero.
or El banquero reembolso nuestro dinero. Deposito or reembolso could fit well. hope that helps.