单项选择题

Foreign exchange receipts of domestic entities for current account transactions shall be repatriated home and shall not be deposited abroad. Foreign exchange receipts for current account transactions shall be sold to the designated foreign exchange banks, in accordance with the regulations issued by the State Council on the sale, purchase, and payment of foreign exchange, or be deposited in the foreign exchange account upon approval. Foreign exchange for current account payment and transfers may be purchased from designated foreign exchange banks upon the presentation of valid documents and commercial bills.
After the foreign exchange restrictions on current account transactions were lifted in 1996, cases of fraud of foreign exchange have increased significantly. To address such problems, the SAFE has taken enforcement actions. To enforce the surrender of export proceeds, the SAFE and its local branches undertake to verify collection of export earnings. When exporting goods abroad, domestic exporting entities are required to undergo the verification procedures. The customs offices shall accept and handle declaration for export based on verification certificate within validity period. Only after no mistakes are found in the examination can customs permit entrance and clearance. After goods have been shipped out of Chinese territory, the customs shall write their opinion and stamp with "proof seal" on the verification certificate, with which the exporter goes through verification procedures. The exporter must send the stub of verification certificate together with commercial invoices and declaration form to the SAFE within 60 days of the date of customs declaration. The export earnings are then surrendered to designated banks or entered the exporter"s foreign exchange account. If domestic entities need foreign exchange for current account payment, ______.

A.they can buy it from any foreign exchange banks.
B.they can buy it from the designated foreign exchange banks unconditionally.
C.they can buy it from the designated foreign exchange banks by showing the relevant valid commercial documents.
D.they can buy it from any banks by presenting valid documents and commercial bills.