A.) Scalar quantities must be converted first to have the same units before adding or subtracting.
True. E.g. You don't add 3 minutes to 2 hours and get 5 somethings.
B.) Scalar quantities possess both magnitude and direction.
False. The definition is scalar quantities possess only magnitude.
C.) Scalar quantities can be positive or negative.
True in general - but it depends on the type of scalar.
E.g.
A temperature can be positive or negative, e.g.+15ºC or -35ºC.
But distance between points is always positive.
D.) Scalar quantities with different units may be multiplied or divided with each other.
True.
E.g. move a distance 20m in 5s and you can find the speed = 20/5 = 4m/s.
E.g. move for 2s at 3m/s, and you can find distance = 2x3=6m.
Distance, speed and time are all scalars.
E.) The cargo ship’s pull on a boat is an example of scalar quantity.
False. The 'pull' is a force, so it is a vector - it has a direction (e.g. to the east) as well as a magnitude; this makes it a vector.
F.) The speedometer of a car measures a scalar quantity.
True. The reading gives speed (a scalar), not velocity (speed and direction).