(   ) is a statement of "unconditional order".    
A、"Pay to Company A, provided the goods are produced according to the requirements under the sales contract."
B、"Pay to the order of Company A the sum of USD 6,000 only on delivery of Insurance Policy."
C、"Pay to Company F or order the sum of GBP 2,000 only."
D、"Pay to Company A, provided that the goods are shipped before May 1, 2020."