The answer is D, because X belongs to S, so the square of X must also belong to S, so the square of X should be less than or equal to X, so X cannot be greater than 1, that is, L cannot be greater than1;

Therefore, when the first proposition is m= 1, the value range of x should be 1 to 1, that is,1; So the proposition 1 is correct.

The second proposition when m=-0.5, because the set should contain the square of this number, that is, 0.25, so L should be greater than or equal to 0.25, but not greater than 1, so proposition 2 is also correct;

Proposition 3 because l=0.5, that is to say, both x and the square of x should be less than 0.5, so x should meet the requirements of proposition 3.

So all three propositions are correct.