Does the Interpretation on the Estimated Coefficient on the Treatment

Multiple Choice

Does the interpretation on the estimated coefficient on the treatment change if you use a proxy variable to control for a confounding factor?

A) No, the estimated coefficient is a consistent estimate of the causal effect.
B) No, but instead of getting causal estimate you're only estimating partial correlations.
C) Yes, the coefficient on the treatment is biased.
D) Yes, the coefficient on the treatment suffers from the simultaneity bias.