Final answer:
Spain was concerned about France's exploration of Texas because they feared the French might try to take over the territory.
Step-by-step explanation:
Spain was concerned about France's exploration of the region now known as Texas because they feared that the French might try to take over the territory. France had been actively contesting Spanish power in the Americas and had attempted to establish a colony in Spanish Florida to interrupt Spanish shipping lanes. Spain did not want to lose control over its New World Empire and wanted to prevent the French from expanding their influence in the region.