Sum of two sides can not be smaller than third side and difference of two sides cannot be larger then third side.
Answer is B.
For this case we have the following vectors:

The dot product of two vectors is a scalar.
The point product consists of multiplying component by component and then adding the result of the multiplication of each component.
For the product point of the vectors a and b we have:
Answer:
The product point of the vectors a and b is: