Let L ≤ ML′ denote that language L is mapping reducible (many to one reducible) to language L closed

Question

Let L ≤ _ML′ denote that language L is mapping reducible (many to one reducible) to language L′. Which one of the following is True?

1. If L ≤_PL′ and L′ is semidecidable then L is semidecidable.
2. If L ≤ _PL′ and L is RE then L′ is RE.
3. If L ≤ _PL′ and L is decidable then L′ decidable.
4. If L ≤ _PL′ and L is recursive then L′ is recursive.

Could anyone please solve this and explain the this reducibility logic ?