Abstract. Let G be aﬁnite group and nX a conjugacy class of elements of
order n in G. G is called nX−complementary generated if,
for every x G 
1, there is a y nX
suchthat G =<x,y>.
In [20] the
question of ﬁnding all positive integers n such that a given nonabelian ﬁnite simple group G is nXcomplementary generated was posed. In this paper we answer
this question for the sporadic group Ru.
In fact, we prove that for any element order n of the sporadic group Ru,
Ru is nXcomplementary generated if and only if n ≥ 3.
