题目

READY or not, the college application season has begun. There are two main kinds of early admissions programs: Early Action and Early Decision.             Early Action is a great choice for the well-prepared student. Students apply early, and are allowed to apply under an Early Action program to as many colleges as they choose. The biggest advantage for students is that colleges let them know early – in most cases, before Jan 1. Roughly 15 percent of colleges and universities offer an Early Action option. Oct 15 is now the first deadline for many colleges and universiti用反证法证明命题“在△ABC中，∠A＞∠B，则a＞b”时，第一步应先假设（    ）