nouns - Word can be single or plural and is also possessive at the same time

I am trying to construct a sentence for a printed document that requires an odd usage of a noun that can be singular or plural but is also possessive.

Here is an example of a sentence that contains a noun that could be singular or plural and so both are listed:

Each person selects which task or tasks they would like to complete.

Some people would use task(s) instead of task or tasks. But this is a different issue. I tend to avoid this.

Suppose a related sentence now mentions something belonging to each task. Perhaps a single task is selected at random, we could say the following:

The random number generator decides which single task's requirements are fulfilled.

Here we talk about requirements belonging to one task. But if there is more than one task then we would need to move the apostrophe to after the s. Right?

The list of two or more random numbers decides which tasks' requirements are fulfilled.

Now here is my dilemma, I need to talk about a list of tasks that could contain a single item. Is it appropriate to use the plural?

The list of one or more random numbers decides which ?????? requirements are fulfilled.

I'd like to avoid using something like the following which appears to me as if it is technically correct but sounds wrong:

The list of one or more random numbers decides which task's or tasks' requirements are fulfilled.

Answer

I think you should just use the plural which tasks'. Using a plural doesn't always mean that there will be more than one of the item. It's often used when this is just a possibility. For instance, if you said

We'll give out prizes to all the people who show up.

you would not be considered incorrect if only one person shows up (at least not grammatically -- you might still have a marketing problem).

In your case, since you specify one of more at the beginning, and that these correspond directly to the tasks, it's clear that the number of tasks can be one of more.