When the C$++$ RedBlackTree's TryCase$4()$ function returns true, the number of black nodes on the path from the root to node has $\_\_\_\_\_.$

bool TryCase$4($RBTNode$*$ node, RBTNode$*$ sibling$)\{$ if $($node$->$parent$->$IsRed$()$ && sibling$->$AreBothChildrenBlack$())\{$ node$->$parent$->$color $=$ RBTNode::BLACKCOLOR; sibling$->$color $=$ RBTNode::REDCOLOR; return true; $\}$ return false; $//$ not case $4\}$

Group of answer choices

decreased by $1$

decreased by $2$

increased by $1$

increased by $2$