A. where
B. when
C. so
D. how

A. had informed
B. had been informed
C. has informed
D. has been informed

     During the past few years,scientists the world over have suddenly found themselves productively
engaged in the task they once spent their lives avoiding-writing,any kind of writing,and particularly letter 
writing.Encouraged by electronic mail's surprisingly high speed,convenience and economy,people who
never before touched the stuff are regularly,skillfully,even cheerfully tapping out a great deal of
correspondence.
     Electronic networks,woven into the fabric of scientific communication these days are the route to
colleagues in distant countries to share data,bulletin boards and electronic journals.Anyone with personal
computer,a modem and the software to link computers over telephone lines can sign on.An estimated five million scientists have done so with more joining every day,most of them communicating through bundle of
interconnected domestic and foreign routes known collectively as the Internet,or net.
     E-mail is starting to edge out the fax,the telephone,over-night mail,and of course,land mail.It shrinks
time and distance between scientific collaborators,in part because it is conveniently asynchronous (writers
can type while their colleagues across time zones sleep;their message will be waiting).If it is not yet
speeding discoveries,it is certainly accelerating communication.
     Jeremy Bernstei,the physicist and science writer,once called E-mail the physicist's umbilical cord (生命线).Lately other people,too,have been discovering its connective virtues.Physicists are using it;college
students are using it;everybody is using it,and as a sign that it has come of age,the New Yorker has
celebrated its liberating presence with a cartoon-an appreciative dog seated at a keyboard,saying
happily,"On the Internet nobody knows you're a dog."