All the vectors quantities obey:
(a) Parallelogram law of addition
(b) Parallelogram law of multiplication
(c) Parallelogram law of addition of square root of their magnitudes
(d) Parallelogram law of addition of square of their magnitudes
This question was posed to me during a job interview.
The doubt is from Addition of a System of Coplanar Forces in chapter Force Vectors of Engineering Mechanics