You create a data block based on a relational table containing a REF column. You select the REF column for your form module. What is true about the items based on the REF column attributes?（）

• A、The Query Only property is set to Yes. 
• B、The Conceal Data property is set to Yes. 
• C、The Insert Allowed property is set to Yes. 
• D、The Update Allowed property is set to Yes.