Assume the Analysis of Friedman and Phelps Is Correct, So

Assume the analysis of Friedman and Phelps is correct, so that the following equation is valid: ​
Unemployment rate = Natural rate of unemployment − a × (Αctual inflation − x) .
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In this equation,

A) a is a parameter that measures how much actual inflation responds to expected inflation.
B) a = 0 at the point of intersection of the short-run and long-run Phillips curves.
C) x is the expected rate of inflation.
D) x = 0 when the actual rate of inflation equals the expected rate of inflation.