Here's why:
* Born in France: He was born in Rouen, France, in 1643.
* French Exploration: He was a prominent figure in French exploration of North America.
* Official Language: French was the official language of the French colonies at the time.
It's also possible he had some fluency in Indigenous languages. He spent considerable time interacting with Native American tribes during his expeditions. Learning their languages would have been crucial for trade, alliances, and navigation. However, there is no specific evidence of which languages he learned.
Therefore, we can say with certainty that Robert de La Salle spoke French, but his knowledge of Indigenous languages remains a matter of speculation.