Answer: Light
Explanation: Light can travel in empty space or vacuum. It doesn't need any medium to which it travels.
Animals with bilateral symmetry can be divided equally along only one plane.
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You can draw a free body diagram with two 250N forces acting on the human, one from each side. The net force is 0 because the two applied forces cancel each other out since they are in opposite directions.
Th correct answer would be D! Hope this helps