The correct reason for why Ferdinand Magellan sought financial support in Spain for his voyage is:
King Manuel of Portugal denied Magellan financial support for his expedition to find new routes to Asia for trade.
After having trouble securing support from the Portuguese crown, Magellan, who had previously served under King Manuel I of Portugal, turned to Spain. He sought sponsorship from King Charles I of Spain, believing that he could find a westward route to the Spice Islands (Maluku Islands) and capitalize on the lucrative spice trade. This decision ultimately led to his famous voyage that circumnavigated the globe.