Newton's first law

Two students want to determine the inertial mass of a block. Student A hangs the block from a spring scale. Student B places the block on a near-frictionless surface and measures the block’s acceleration while applying a known horizontal force.

Which student’s method is best for measuring inertial mass, and why?

(Choice A)
Student A's, because they are measuring the mass of the block using $F_{g}$ ‍ and dividing by the known acceleration of gravity at the surface of Earth.
(Choice B)
Student B's, because they are measuring horizontal force on the block, not the vertical force.
(Choice C)
Student A's, because they are measuring vertical force on the block, not horizontal.
(Choice D)
Student B's, because they are applying a force, measuring the non-gravitational acceleration and calculating the mass.

AP®︎/College Physics 1

Course: AP®︎/College Physics 1 > Unit 2

Problem