The correct answer is D) Brazos River.
Spain's recommended route to north New Spain followed the original route of Andres do Campo, which follows the Brazos River.
That is why Spanish explorers and frays continued their exploration of the new territories.
Andres do Campo was a Portuguese explorer, who participated in the Coronado expedition of Spanish conquerors. After the assassination of Fray Juan de Padilla by the Native Indians, Campo tried to escape and survive under harsh conditions. He traveled down to the territories of México, until he arrived at the Panuco River, in the Mexican state of Veracruz, in that time, New Spain.