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1. Phase margin φ_PM is directly proportional to damping ratio ξ
2. Phase margin φ_PM is inversely proportional to damping ratio ξ
3. Phase margin φ_PM and damping ratio ξ are unrelated.
4. When phase margin φ_PMis 0, damping ratio ξ is 0.

Correct Option: A

The phase margin, φ_PMand damping ratio, ξ is related by equation

ξ =	tan φ_PM√cos φ_PM
	2

thus, from this relation we conclude that
● Phase margin φPM is directly proportional to damping ratio.
● When phase margin, is 0, damping ratio, ξ is 0.