Let $S_n$ stand for "There are at least n materials objects".
First I am asked, using the dictionary Q: ...is a material object, to provide a definition of $S_0$. This seems like a non-question to me - surely it states nothing? I have considered something like $\exists xQx\lor\lnot\exists xQx$ which is obviously a tautology. Do you think this is what they are looking for?
Past this it asks for me to specify (recursively or otherwise) to specify an $L_=$ sentence for $S_n$.
Thanks for your help!