What is wrong with the following code?

public static char grade$($int score$)$

$\{$

if $($score $>=9)$

$\{$

return $\text{'}$A$\text{'}$;

$\}$

else if $($score $>=8)$

$\{$

return $\text{'}$B$\text{'}$;

$\}$

else if $($score $>=6)$

$\{$

return $\text{'}$C$\text{'}$;

$\}$

else if $($score $>4)$

$\{$

return $\text{'}$D$\text{'}$;

$\}$

else if $($score $<4)$

$\{$

return $\text{'}$F$\text{'}$;

$\}$

$\}$

Group of answer choices

Invalid parameter variable type

No return statement for all logic paths

Invalid argument in return statements

Illegal parameter variable name