— Well, they have set out to deal with the present situation ________ they think deserves their immediate attention.
A:what
B:where
C:when
D:which
①氢元素____②氧元素____③铁元素____④镁元素____ ⑤氧气____⑥氮气____⑦铜____⑧锌____ ⑨水____⑩二氧化硫____
在横线上填上适当的数。
4 - ____ = 0 ____ - 0 = 5 0 + ____ = 3
2 + ____ =2 ____ + ____ = 0 ____ - ____ = 0
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.