If the proposition (1) is true, then (2) take the inverse proposition "At least one of Wang X and Liu X knows computers" and (3) take the inverse proposition "Everyone in the class knows computers". The three propositions are not contradictory, and the final conclusion is that everyone in the class knows computers. Therefore, the study committee understands computers.
If proposition (2) is true, then (1) takes the inverse proposition "No one in the class knows computers" and (3) takes the inverse proposition "Everyone in the class knows computers", and the two inverse propositions conflict, so the assumption is not established.
If the proposition (3) is true, then (1) takes the inverse proposition "No one in the class knows computers" and (2) takes the inverse proposition "At least one of Wang X and Liu X knows computers", and the two inverse propositions conflict, so the assumption is untenable.