Questions & Answers about Bawełna, wełna i len są na stole.
Because the sentence has a compound subject: bawełna, wełna i len = cotton, wool, and flax/linen.
Each noun is singular by itself, but together they form a plural subject, so Polish uses the plural verb są = are.
- bawełna jest = cotton is
- wełna jest = wool is
- len jest = flax is
- bawełna, wełna i len są = cotton, wool, and flax are
Because after na with the meaning on in a static location, Polish uses the locative case.
So:
- stół = table (dictionary form, nominative)
- na stole = on the table (locative)
Compare:
- na stole = on the table, already there
- na stół = onto the table, movement toward it
In your sentence, the things are already on the table, so na stole is correct.