Question (not refined Product Backlog, Sprint planning)?

Q1:
How should we react if we realize at Sprint Planning Meeting that the prodcut backlog is not enough refined (clear)? It has impact on Dev Team's forcasting. for sure the PO must be coach to prevent such situation for future sprints. I can imagine following 3 ways:

A) We postpone the Planning meeting until we get first clarity for the top PBI in an extra refinement session because these are the most valuable Items and are important to be implemented first.

B) we keep the sprint planning meeting as planned and the Dev. team forcast roughly despite these ambiguities; and they adjust the scope (commited work) if necessary later during sprint with PO agreement

C) to remark such PBI on the top of Product Backlog list as "not ready" and ignore them for the current sprint . The dev. team pulls only PBI which are ready.

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Q2: Do you use similar to DoD , DoR (Definition of Ready) in your project for PBI ?
If yes, could you please share your DoR ?

Thanks,
Mehdi