Teacher:In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".
Teacher: Now, understand the problem? Solve this instance: [header] How to use a graphic flight computer to find ground speed and true heading [title] Align the wind direction under the " true index " mark by rotating the azimuth plate. [step] If the winds are from 330 at 20 knots, align 330 under the true index. [title] Align the grid so the center grommet is over one of the heavy lines. <sep> (A) [step] Only if you are flying with the reverse rotor or with the stick, the grid should be perpendicular to the ground. [title] Align the grid so it is above one of the strong lines, connected to the main mast. (B) [step] It doesn't matter which line is used at this point. [title] Mark the wind speed by counting up from the center grommet. (C) [step] The grid turns when the wind is consistently southeast away from the ground. [title] Position a heavy line going in the direction of the ground. (D) [step] If the wind is coming from east then do not align the grid. [title] Locate the " left terminal " mark on the ground and press it with the tire iron (that is, a large metal tube that sticks out from the ground).
Student:
B