Q: Which of the following can be inferred about U.S. employers of Mexican immigrants?
(B) Some of these employers violate wage laws. // CORRECT. If some of these immigrant workers are accepting wages "well below the U.S. minimum wage," their American employers must be violating wage laws (i.e. paying wages below what the U.S. minimum wage requires).
"...are often more than willing to work for wages well below both the U.S. minimum wage and the poverty line."
Willing does not imply that they are actually accepting wages below the minimum wage, does it?
Also, about option D:
(D) Without Mexican immigrants, some of these employers would be forced to close their businesses. // The passage does not suggest that, without labor from Mexico, these employers will be forced to close. This answer is both too predictive and outside the scope of the argument.
"For years, U.S. employers have counted on a steady flow of labor from Mexico willing to accept low-skilled, low paying jobs."
"Counted on" makes Option D sound much more viable than Choice B to me... could you please explain the test maker's rationale behind this?