1. Recursive languages are closed under concatenation.
2. Recursive languages are closed under quotient with regular language.
Let's assume
L3 = {#}. ------> regular because finite. Hence recursive.
L4= L1.L3 = {wi# : wi belongs to L1)
L4 is recursive. (1)
L5= {#}.L1 ----> recursive (1)
S1: given L1 is recursive
Therefore L2=L4.L1 is also recursive. (1)
Hence S1 is true.
S2: given L2 is recursive
Therefore L1= L2/L5 is also recursive. (2)
S2 is true as well.
ANSWER: (a)