If $X, Y$ and $Z$ in figure are identical lamps, which of the following changes to the brightnesses of the lamps occur when switch $S$ is closed?
  • A$X$ stays the same, $Y$ decreases
  • B$X$ increases, $Y$ decreases
  • C$X$ increases, $Y$ stays the same
  • D$X$ decreases, $Y$ increases
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