Solution: ∠ 1 and ∠3 are internal angles formed by l 1 and l2, so we can judge the straight line L1∑ L2;

∠ 4 and ∠ 5 are congruent angles formed by l 1 and l2, so we can judge the straight line L1∨ L2;

∠2 and ∠ 4 are ipsilateral internal angles formed by l 1 and l2, so we can judge the straight line L1∨ L2;

∠2 and∠ 3 are not angles formed by l 1 and l2, so the straight line l 1∨L2 cannot be judged.

So choose B.