Please choose one and only one which is the wrong statement, or the least correct.

$($a$)$ Each system $($internally$)$ defined error has its own error code $($number$),$ and an error message.

$($b$)$ Once an Oracle system $($internally$)$ defined error occurs in a program, the system engine will automatically raise this exception.

$($c$)$ When a user$-$defined exception is initially defined, it always has an individual name and a code number of $+1.$

$($d$)$ A user defined exceptions should be defined in the declarative section.

$($e$)$ Among thousands system internally defined exceptions, there are around $23$ are given names by the system. For these $23$ exceptions with name, the system will not detect and raise these errors any more.

Part III. $(20$ points $**4$ questions $=$ total $80$ points