The criterion of constraint of a chain connecting the number of binary joints (J) number of higher pairs (H) and the number of links is : J +$\frac{H}{2}=\frac{3L}{2}-2$ 
When is the chain locked?
(a) L.H.S = R.H.S (b) L.H.S > R.H.S
(c) L.H.S < R.H.S (d) The chain will never get locked