2-6：PE=mgz，where z = the ___________ above horizontal reference plane
举一反三
- A horizontal plane divides the body into which of the following?
- In holography, the picture wave and reference wave must be plane wave.()
- In holography, the picture wave and reference wave must be plane<br/>wave.()
- The plane flew ________ the clouds. A: by B: down C: behind D: above
- There is a plane flying ____ your head. A: on B: below C: over D: above