The correct answers are B, C, and D.
B: the measure of < QLP is 50°.
C: < NLO (30°) and < OLP (40°) share the same vertex, L, and their measure add up to < NLP = 70°.
D: < QLP (50°) + < PLO (40°) = 90° (complementary angles). Their sum is the same as the sum of the measure of < MLN (60°) + < NLO (30°) = 90°.
Therefore, the correct answers are options B, C, and D.