乌梅丸的主治病证是（）

A.痰厥

B.蛔厥

C.气厥

D.血厥

E.晕厥

In the foreign trade business, the payment is always made by L/
C．In this sentence, L/C is the abbreviation for ______.

A．bill of Lading
B．commercial Invoice
C．buying Contract
D．letter of Credit