A label can be used for which of the following?

A label can be used for which of the following?

as an alias for a register

to define a new assembly language directive created by assembly language programmers

as an alias for the CPU Control unit

to mark an assembly language line that any j instruction can jump to

for storing the type of instruction being executed $($that is$,$ I$-$type, J$-$type, or R$-$type$)$