Grouping of options at 2 levels

Framing of options at 2 level - how to link. at first level I provide list of districts - how can i link block to districts ?

Hi @gnu_upadhyay
welcome to the forum! Please introduce yourself here!

your question is very laconic it would be better if you add more details/samples.
I guess are talking about cascading selects but I'm not sure.