What can you infer about Roman society based on the first law from Table XI, “Marriages should not take place between plebeians and patricians?”

You can infer that their social hierarchies were very strict. The law shows how they liked to keep the poorer people with the poor and the richer with the rich, rather than possibly allow them to intermingle and mix. The fact that it's the first law on Table XI also shows how important such a law was to them.

what are the choices?

that is probably something for you to answer