As per the passage the main concern is dropping of Mexican nationals due to rise in tuition for international and out-of-state students from $40 to $120 per credit hour.
So, to alleviate this drop out issue , if possible tuition fee must be reduced to some level.
If we go through the choices :
(A) Providing grants-in-aid to Mexican nationals to study in Mexican universities. -- The problem is drop out of Mexicans , we need to bring the students to Texas again , so clearly not correct.
(B) Allowing Mexican nationals to study in Texas border colleges and to pay in-state tuition rates, which are the same as the previous international rate -- this will indeed correct as this talks about decrease in tuition fees.
(C) Reemphasizing the goals and mission of the Texas state border colleges as serving both in-state students and Mexican nationals -- The goals and mission is not what the paragraph is talking about and it will not solve the issue for not correct.
(D) Increasing the financial resources of Texas colleges by raising the tuition for in-state students attending state institutions -- raising tuition fees of in-state students , here we are only talking out international i.e. Mexican students so not correct.
(E) Offering career counseling for those Mexican nationals who graduate from state border colleges and intend to return to Mexico. -- We are not talking about graduates , students are not taking admission due to tuition fees, so clearly not correct.
So, the ans is B