10.y = sin2x+cos2x = √ 2sin (2x+π/4) Period T=2π/w (w=2 from the question), so period T=π. Choose B.

19. Find a probability of 0.4m. We can find the probability that both segments are greater than 0.4m, and then subtract the answer from 1. When the length of both sections is 0.4m ~ 0.6m, the requirements are met, so the probability that both sections are greater than 0.4m is 0.2; Therefore, the probability that a segment is less than 0.4m is 1-0.2=0.8, so B is selected.