Answer
PSII produces oxygen, which can be used by rubisco for photorespiration. That in turn reduces photosynthetic efficiency and output, so by moving PSII away from rubisco, $C_{4}$ plants become more photosynthetically efficient.
Work Step by Step
This question is asking you to make a connection between the light reactions and the Calvin cycle, specifically with reference to photorespiration. This explains the placement of PSII in $C_{4}$ plants as they try to make rubisco/photosynthesis more efficient.
