A Shift from S₁ to S₂ Reflects the Change That $P _ { 1 }$

Multiple Choice

A shift from S₁ to S₂ reflects the change that happens when a negative externality is taken into account.A shift from D₁ to D₂ reflects the change that happens when a positive externality is taken into account.
-Refer to the above figures.Externalities exist in both panels.After correcting for the externalities the prices should be

A) $P _ { 1 }$ and
$\mathrm { P } _ { 3 }$ .
B) $P _ { 1 }$ and
$\mathrm { P } _ { 4 }$ .
C) $P _ { 2 }$ and
$\mathrm { P } _ { 4 }$ .
D) $P _ { 2 }$ and
$\mathrm { P } _ { 3 }$ .