Question

What is the correct possessive form of the bold words if they are showing joint ownership? Formed, in part, from the Rio Grande, the United States and Mexicos border stretches 1,900 miles long.
United State’s and Mexico’s
United States’ and Mexico’s
United States’s and Mexico’s
United States and Mexico’s

Answer 1

United States' and Mexico's(B)

Answer 2

The correct answer would be the United States and Mexico's because it is asking for joint ownership