by 15 percent/ at 15 percent有什么区别
问题描述:
by 15 percent/ at 15 percent有什么区别
答
by 15 percent指的是 (上升或下降了)15%
at 15 percent指的是 (上升或下降到)15%
至于是上升还是下降,这要看上下文的语境了.