apply the given condition of connectivity to 2 bits..00==>01==>11==>10==>00
for 3 bits..image in comment box
ACTUALLY IT IS A N CUBE...
vertex of n cube=n;
degree of n cube=n;
edges of n cube=n*2^(n-1)
chromatic number=2(ALWAYS)
hence chromatic number of the graph=2
now diameter of graph=number of bits =5
thus ratio =2/5