The best-supported opinion from the information provided in your question is:
Spain was motivated to explore Texas because French territory bordered Spanish settlements and created competition for land.
This assertion reflects the geopolitical dynamics of the era, where the presence of French territories posed a threat to Spanish claims and interests in the region, prompting Spain to increase its exploration efforts to assert its dominance and secure its territories.
The other options either exaggerate the effects of exploration (like claiming complete elimination of competition or complete control of all land) or oversimplify the motivations behind Spanish exploration by suggesting equal importance of all three reasons without specific evidence.