a). for velocity, you must have a number, a unit, and a direction. Yes. This one isn't bad. The 'number' and the 'unit' are the speed.
b). the si units for velocity are miles per hour. No. That's silly. 'miles' is not an SI unit, and 'miles per hour' is only a speed, not a velocity.
c). the symbol for velocity is . You can use any symbol you want for velocity, as long as you make its meaning very clear, so that everybody knows what symbol you're using for velocity. But this choice-c is still wrong, because either it's incomplete, or else it's using 'space' for velocity, which is a very poor symbol.
d). to calculate velocity, divide the displacement by time.
Yes, that's OK, but you have to remember that the displacement has a direction, and so does the velocity.
B) in Physics, charge conservation is the principle that the total electric charge in an isolated system never changes. The net quantity of electrical charge, the amount of positive charge minus the amount of negative charge in the universe is always conserved.
