Final answer:
The Spanish considered the French a threat in 1699 due to French settlements in Biloxi Bay and their western exploration, challenging Spanish territorial claims. The correct answer is option C.
Step-by-step explanation:
The Spanish felt that the French posed a threat again in 1699 because C. The French had settled in Biloxi Bay and were exploring to the west. This active French presence on the Gulf Coast threatened Spanish claims in the region and their control of shipping lanes coming north out of the Caribbean. The French intentions to establish colonies and explore further into areas claimed by Spain posed significant risks to Spanish sovereignty over their New World territories.