Read the scenario.
a car moves 30 mi/h to the north. every second, the velocity increases by 3 mi/h.
which option represents the acceleration as a vector quantity?
3 mi/h/s
30 mi/h
30 mi/h north
3 mi/h/s north

3 mi/h/s north I would say.

Explanation:

Since vector quantities always have a direction (north for example) it must be either the last or second last option.

And since the question is asking 'which option represents the acceleration as a vector quantity?' we can ignor the 30 mi/h north since that has the the initial velocity (which we don't care about in this question)

So remember the differerence between Scalars and Vectors.

Scalars have only size (magnitude) like speed for example.

Vectors have a size (magnitude) and a direction like acceleration for example.

Speed is a scalar because you can say "50 mi/h" without saying in which direction. Time is also a scalar.

Acceleration and velocity are examples of Vector quantities because in your answer you must say in which direction an object is travelling "3m s⁻² to the north" (m s⁻² means meters per second per second)

change tension

a.   mass number from atomic number