发盘必须明确规定有效期限，未规定有效期的发盘无效。
Weare_______acopyofourcatalogueforyourreference.
A、send
B、covering
C、closed
D、enclosing
Yourdelayinshipmentwill______usingreatdifficulty.
A、cause
B、lead
C、conclude
D、involve
Wewouldliketotakethis______toestablishbusinessrelationswithyou.
A、opening
B、opportunity
C、step
D、advantage
Ourcustomersfindyourgoodsquite______.
A、satisfied
B、satisfaction
C、satisfactory
D、satisfy