Which of the Following Are True About a Bourdon Gauge

Which of the following are true about a Bourdon gauge?
1) It is always used with an adjustable high-pressure reducing valve.
2) It actually senses pressure but is calibrated to display flow.
3) It reads a flow higher than actual if downstream pressure increases.
4) It will register zero flow when the outlet is completely blocked.

A) 1 and 3 only
B) 1, 2, and 3 only
C) 3 and 4 only
D) 2, 3, and 4 only