Answer: b) 10 m/s down
Step-by-step explanation:
Let's start by explaining that a vector is one that has a numerical value along with its units (called a module) and a direction, while a scalar is only determined with a number and its corresponding units, without direction.
Then, if we are given a quantity with only a numerical value along with its units we will have a scalar, and when we have a quantity with its numerical value along with its units and also the direction is given, we will have a vector.
So, according to this explanation, the only option that fullfils the conditions of a vector is b:
10 m/s down
Because we have a numerical value (10) with ist units (meters per second) and its direction (down).