I think you are referring to Section X, Question 5. Correct? If so it's easier than you think.
Don't put "d. an organization supporting..." While PTO's do provide supplemental support to schools, that's not what the IRS means. That typically refers to much more substantative involvement, such as underwriting the costs so the supported organization can exist. More than the extras the normal PTO provides.
I think most of us put "h". But we've seen g, h, or i all selected with success.
g) 509(a)(1) and 170(b)(1)(A)(vi)—an organization that receives a substantial part of its financial support in the form of contributions from publicly supported organizations, from a governmental unit, or from the general public.
h) 509(a)(2)—an organization that normally receives not more than one-third of its financial support from gross investment income and receives more than one-third of its financial support from contributions, membership fees, and gross receipts from activities related to its exempt functions (subject to certain exceptions).
i) A publicly supported organization, but unsure if it is described in 5g or 5h. The organization would like the IRS to decide the correct status.