$L\leq _{M}L'$
If L is undecidable then L' is also undecidable.
If L' is decidable or semi decidable then L is also decidable or semi decidable.
Checking options
A)L' is semidecidable so L is also semidecidable.
it satisfies above property
B)L is RE it is semidecidable then we cannot say about L'
C)L is decidable we cannot say what is L'
D)L is recursive ,it is decidable.same as above.
Hence option should be A.
