The pressure less than atmospheric , pressure, is known

ANS:D - all the above.

1. Suction pressure: This term is commonly used, especially in contexts where a fluid is being drawn or sucked into a system by means of a pump or other suction device.
2. Vacuum pressure: Vacuum pressure refers to pressure levels below atmospheric pressure. It's often used in the context of vacuum systems where the pressure is intentionally reduced below atmospheric pressure.
3. Negative gauge pressure: Negative gauge pressure is a term used to describe pressures below atmospheric pressure as measured by a gauge. It represents pressure less than atmospheric pressure but is typically displayed on a gauge as a negative value relative to atmospheric pressure.