If s=abcd is a string defined over σ = {a, bc, d}then reverse of s is dcba.
δ true
δ false

True

Explanation:

If s=abcd is a string defined over {a,b,c,d}, it corresponds to a regular expression which can be represented using a finite automata. Then the reverse of the string essentially corresponds to another finite automata where the starting state becomes the accepting state and vice versa.Moreover all the directions of state transitions will be reversed for each of the transitions in the original automata.

With these modifications, the new finite automata will accept a string which is reverse of the original string ,namely, dcba and this string will ne part of the reverse language.

its true for the one time