In this particular case, the policyholder is paying a premium for the whole of their life to the insurer.
There are two things to consider here:
1. To pay for a particular benefit - you pay a premium to the insurer for them offering you the "insurance" product. This can be in the form of a series of payments- so an annuity.
2. These insurance products can be all sorts of things - but one of them can be an annuity that the insurer gives you.
So you see, both the premium and the benefit can be an annuity! It depends on what the question asked. An annuity is just a way of expressing a series of payments. Seeing as both the benefit and the premium can be a series of payments - both can be an annuity.