1. an object is moving in a straight line at constant speed. which of the following is true?
there are no forces acting on the object.
the object has 0 acceleration.
the object has constant velocity.
a. i only
b. ll only
c. ii and iii only
d. i, ii, and iii

c. II and III only (the object has 0 acceleration and the object has  constant velocity.)

Why?

Let's discard each of the given options to find the correct one(s).

False, if an object has a constant speed, it does not mean that there are no forces acting on it, in fact, there will be always acting forces, like frictional force, gravity force, air resistance, and others.

True, in an object is moving at constant speed, it means that there is no acceleration, the speed will be the same all the time during motion.

True, if an object is moving in a straight line at constant speed the velocity will be also constant. The velocity of an object is referring to its speed and its direction, if the object is moving in a straight line, the direction will be the same, so, if the speed is constant, the velocity will be also constant.

Have a nice day!