For how many primes p less than 15, there exists integer triples (m,n,k) such that
m+n+kmn+mk+nkmnk≡≡≡0(modp)1(modp)2(modp).<spanclass=′latex−bold′>(A)</span> 2<spanclass=′latex−bold′>(B)</span> 3<spanclass=′latex−bold′>(C)</span> 4<spanclass=′latex−bold′>(D)</span> 5<spanclass=′latex−bold′>(E)</span> 6 modular arithmeticquadratics