A unit vector has Magnitude 1

By convention the letters i, j, and k are used to describe 3 unit vectors that are each at right angles to each other.

I am __assuming__ that the person who set your question is using this convention.

If you go one unit in the i direction,

then one unit in the j direction,

then one unit in the k direction,

then draw a line from the start position to the end position,

This line will represent the vector A.

The length of this line will be the Magnitude of A.

Using Pythagoras (square root of the sum of the squares of the sides)

will show that the Magnitude of A will not be greater than 1

Similarly for B (but in the opposite direction).