[A] To create an SQ, you need to fill the field called Enquiry Number.
[B] Sales Quotations are created against Request for Quotations (RFQ). You have to enter the RFQ number in this field, or the number mentioned on any other document which forms the enquiry against which the SQ is created.
[C] If the counterparty as requested for a quotation over the phone or mail then you can also type that in that field
[D] If the SQ is being punched against an RFQ sent, then the enquiry number will already be filled by that RFQ number.