The force of gravity pulls all objects downwards." which of these statements is correct about this law of science? a. it is not supported by observations. b. it can be contradicted by valid data. c. it is an observation which cannot be explained. d. it is a description in nature which cannot remain unchanged.

d. it is a description in nature which cannot remain unchanged.

Explanation:

The force gravity refers to the force due to the acceleration of gravity, which is towards the nucleus of the Earth.

Now, it's known that the force of gravity pulls all objects downwards. But, this is relative, because depending on the point of reference downwards can also refers to upwards. In other words, if you consider it from the space, you will see deduct that there's no directions at all, in fact, there you would realize that gravity is just an atraction force, not just a downward force.

That's why the right answer here is d., because the force of gravity is a description of the nature, because a truly explanation of the matter is not clear yet (modern physyics is looking for that), and "cannot remain unchanged", because the downwards direction depends on where we at.

therefore, the efficiency is:

You need to be more specific.  i really don't know what a "motion map" is.you can draw a graph of an object's position, distance, displacement, speed,velocity, or acceleration versus time, or you can draw a graph of the object's x-position versus its y-position and not give any information about time at all.if the graph presents position or displacement against time,  then constant velocity is a straight line . . i.e. a line that has  constant slope.if the graph shows speed against time, then constant velocityis a horizontal piece of line.if the graph shows acceleration against time, then constant  velocity is a piece of line that lies on the x-axis . . it's value is zero.