Next month, Mexico seeks to enter into a treaty with the State of Texas over water rights involving the Rio Grande. Is this treaty constitutional under the U$.$S$.$ Constitution?

a$.$ No$,$ unless it is entered into directly between the President of Mexico and Governor of Texas.

b$.$ No$,$ a treaty is an agreement among independent nations and Texas is not an independent nation.

c$.$ Yes, because Mexico and Texas share the Rio Grande as a boundary.

d$.$ Yes, because Mexico is an independent nation: