According to the passage, Houston aimed his legislative challenge at the graduate and professional school level on the basis of the assumption that A. the greatest inequities existed at the highest academic and professional levels B. the separate-but-equal doctrine applied solely to the highest academic levels C. there were clear precedents for reform in existence at the graduate school level D. the judiciary would feel less apprehension at desegregation on the graduate level E. the consequences of desegregation would become immediately apparent at the graduate school level