While Flying Horizontally in an Airplane, You Notice That a String

Multiple Choice

While flying horizontally in an airplane, you notice that a string dangling from the overhead luggage compartment hangs at rest at $15 ^ { \circ }$ away from the vertical toward the front of the plane.
Using this observation, you can conclude that the airplane is

A) not accelerating because the string is at rest.
B) moving forward.
C) accelerating forward.
D) moving backward.
E) accelerating backward.