An Italian explorer hired by the French to explore the coast of North American and look for the fabled Northwest Passage.

French explorer who found and explored the St. Lawrence Seaway.
A French priest who helped discover the headwaters of the Mississippi River.
A French explorer who helped discover the headwaters of the Mississippi River and follow the river south to Arkansas.
A French explorer who was the first European to follow the Mississippi from its beginning to the Gulf of Mexico.

Giovanni da Verrazzano

Jacques Cartier
Jacques Marquette
Louis Joliet
René-Robert Cavelier, Sieur de La Salle

Easy, the rest are all French !

Yes, you're right! All the explorers mentioned after Giovanni da Verrazzano are indeed French explorers.