Anita is an author who submits short poems to magazines. she never knows for sure which poems will be selected for publication, but the more poems she submits, the more likely she is to have a poem accepted. based on what is known about schedules of reinforcement, you should conclude that anita's submission of poems is being reinforced based on a:

The different schedules of reinforcement that the question is asking about are: Fixed ratio, fixed interval, variable ratio  and variable interval.

Those are the four different intervals in conditioning that are usually mentioned.

Those which are "fixed" will be someohow regular, but we can see here that this is not the case here: she cannot expect some regularity in her acceptance rate, as every decision is independent of the other magazine's decisions.

Now it will be variable ratio - the more she submits, the bigger the chance, but at an unpredictable ratio. It won't be variable interval, since time is not relevant here, only the more