What is the printout of the following switch statement?

char ch $=\text{'}$A$\text{'}$;

switch $($ch$)\{$

case $\text{'}a\text{'}$:

case $\text{'}$A$\text{'}$:

System.out.print$($ch$)$; break;

case $\text{'}b\text{'}$:

case $\text{'}$B$\text{'}$:

System.out.print$($ch$)$; break;

case $\text{'}c\text{'}$:

case $\text{'}C\text{'}$:

System.out.print$($ch$)$; break;

case $\text{'}d\text{'}$:

case $\text{'}D\text{'}$:

System.out.print$($ch$)$;

$\}$

$ab$

A

aa

$abc$

abcd