Question $1$

If the characters $\text{'}{D}^{\text{'}}=>{?}^{\text{'}}{C}^{\text{'}}=>{?}^{\text{'}}{B}^{\text{'}}=>>{?}^{\text{'}}{A}^{\text{'}}$ are placed in a queue $($they arrive in the order right to left$),$ and then removed one at a time, in what order will they be removed?

$\text{'}$D$\text{'},\text{'}$C$\text{'},\text{'}$B$\text{'},\text{'}$A$\text{'}$

$\text{'}$A$\text{'},$ B$\text{'},\text{'}$C$\text{'},\text{'}$D$\text{'}$

$\text{'}$D$\text{'},\text{'}$C$\text{'},\text{'}$A$\text{'},\text{'}$B$\text{'}$

$\text{'}$A$\text{'},$ B$\text{'},\text{'}$D$\text{'},\text{'}$C$\text{'}$