I came across a question which reads
"Suppose the spin degree of freedom of two particles (nonzero rest mass and nonzero spin) is described completely by a Hilbert space of dimension twenty one. Which of the following could be the spin of one of the particles?
(a) 2
(b) 3/2
(c) 1
(d) 1/2"
I am confused about the basics behind this problem; how can we relate spin degrees of freedom with dimensions of Hilbert space?