题目

The machines in this new factory seem to be _________ones in this area. A . modern B . more modern C . most modern D . the most modern 答案：D如图, O为Rt△ABC内切圆, ∠C=90°, AO延长线交BC于D点, 若AC＝4, CD="1," 则⊙O半径为（　　）A．B．C．D．