Use for a napkin only for your（）.

A.before contract or confirmation is signed by buyers and sellers
B.when the buyers want to open a letter of credit
C.when the buyers and sellers finished the transaction
D.after contract or confirmation is signed

A.go with someone as a partner
B.go with someone as a gurd
C.go with someone as an escapee
D.go with someone as an adviser

A.The knife and the fork are switched
B.The fork is laid down；and the knife is put ahead
C.The fork is switched back to the right hand
D.The knif and the fork are never switched