A:x2+3x+4=0
B:x2+4x﹣3=0
C:x2﹣4x+3=0
D:x2+3x﹣4=0
选出不同类别的单词。
(____)1. A. plate B. how C. cake
(____)2. A. some B. many C. how
(____)3. A. is B. one C. three
(____)4. A. one B. a C. an
(____)5. A. you B. they C. this
下列仪器能直接在酒精灯火焰上加热的是____ .
A.试管 B.集气瓶 C.量筒 D.____ .