I saw Bill the room quietly and sit behind the door.
A:enter
B:entering
C:come
D:enter into
①通过R1的电流.
②R2的阻值.
①转动粗准焦螺旋 ②转动细准焦螺旋 ③调节光圈 ④转动转换器 ⑤移动玻片