Scientists believe that human evolution______.A．has seldom been accompanied by climatic ch

Scientists now believe that artificial－hip implants, previously thought to be safe, may ac

Some well-known scientists believe that there is not enough oxygen on Mars to ______ human

Scientists and economists A（believe) that human being B（can never) C（use away) all the D（m

It is believed by scientists that traditional med

It is believed by scientists that traditional med

It is believed by scientists that traditional med