Some parasites kill their host, but most do not.
Parasites are organisms which live off a host.
Some organisms which live off a host kill it, but most do not.
Some what which live off a host kill it, but most do not?

(A) offspring
(B) pets
(C) poisons
(D) fungi
(E) Leptospirosis
(F) bacteria
(G) animals
(H) organisms