What is the task performed by the following algorithm?

A: a bit vector $($an array storing only $1\text{'}$s and $\text{'}$s$)$

pos: highest index of array $A$

function $,$ pos $)$

if $(pos<mi\; id="EditorElement\_93759"></mi><mi\; id="EditorElement\_93761">)</mi>$

return $$

if $($pos$0$ or pos$-1]==1$ or $A[pos+1]==1)$

return $,$ pos$-1)$

if and $A[pos+1]==0$

return $,$ pos$-1)$

none of the others

returning the number of $0\text{'}$s surrounded by $1\text{'}$s

returning the number of digits surrounded by $0\text{'}$s

returning the number of $0\text{'}$s in the array

returning the number of $1\text{'}$s in the array