Light travels until it strikes an object or moves from one medium to another
a.
in a zig-zag pattern
b.
perpendicular to its source
c.
in an unpredictable way
d.
in a straight line

All electromagnetic waves travel in a straight line (D) until they hit something that reflects or refracts or absorbs them, or until they hit the boundary at the beginning of a different medium.

That includes light, because light is an electromagnetic wave.

number of electrons for neutral cl

c. newton's third law of motion