The material contained inside small tubes in levels to make sure that a surface is true or even usually consists of ___________.
A. mercury
B. water and oil
C. a type of liquid and an air bubble
D. sand
The material contained inside small tubes in levels to make sure that a surface is true or even usually consists of ___________.
A. mercury
B. water and oil
C. a type of liquid and an air bubble
D. sand