王大伯家养了20只鹅，养鸭的只数是鹅的5倍，养的鸭比鹅多多少只？
20×5-20
=100-20，
=80（只）．
答：养的鸭比鹅多80只．
. ---- we will take the conditions into careful consideration ______ you have attached to this contract.
---- Thanks. Wish our future cooperation pleasant.
A．after
B．when
C．what
D．which
何谓药物的半衰期？
