regular expression

DFSM

NDFSM

all of these

Designing computers

Designing compilers

Both (a) and(b)

Developing computers

at least one of the set Si is a finite set

not more than one of the sets Si can be finite

at least one of the sets Si is an infinite set

not more than one of the sets Si can be infinite

Mathematical semantics

Interpretative semantics

Translational semantics

Axiomatic semantics

a* b*

(a | b)*

(ab)+

(a | b*)