Answer:
B.A submarine was 250 meters below sea level...
Step-by-step explanation:
I. Given went down is negative.value, and went up is positive value
 He went down for 250, in one hr, he went up 200 and 50 meters
  = -250 + 200 + 5
  = -250 + 250
  = 0
That means he's already beyond the surface.
Hope that help :)