Why Does It Make Evolutionary Sense That Not Only the Elephant

Why does it make evolutionary sense that not only the elephant mom but also all her female relatives will help her look after her baby?

A) This is kin selection. Families work together for the benefit of all their shared genes.
B) Elephants are known to be very smart, so it makes sense that they would cooperate with each other since they know it benefits everybody.
C) It is too hard to raise a baby elephant for one individual to do it by herself. The herd benefits by gaining another member if everyone cooperates.
D) This is kin selection where the males do not cooperate because for them it is more important to go off and mate more in order to spread their genes around.
E) Actually, it doesn't make sense because those relatives should be more interested in their own offspring according to natural selection.