根据短文内容，从短文后的七个选项中选出能填入空白处的最佳选项，选项中有两项为多余选项。
Brain Drain
Imagine you are sitting in your living room and out of surprise you get a call from a friend．He tells you that he's gotten the student visa and is going to study abroad for higher education．His parents may feel it a privilege that their son is guaranteed to have a bright future and unbelievable job opportunities．While many people believe that immigration is a personal choice that must be understood and respected, others have realized a serious problem-brain drain．Brain drain refers to the flow of highly skilled and educated people, such as doctors, engineers, scientists from less developed countries to developed countries． Brain drain has become a common social problem．  These reasons are "Push" factors （因素） and "Pull" factors．The push factors include low wages and lack of satisfactory working and living conditions, and so on．The pull factors, however, include higher pay and better working conditions, better job opportunities, as well as better research equipment．
As we can see, many educated people are heading for richer countries, seeking higher wages and better working conditions． It reduces the number of creative people who can contribute to the development of their country．Meanwhile, with more successful businessmen taking their money abroad, their countries are missing an opportunity of wealth creation．  Besides these economic effects, the brain drain has also social negative effects, such as the loss of improvement in research and technique．
Therefore, measures must be taken in less developed countries to avoid brain drain．  Social developments like health services and education opportunities also need improving．Otherwise, less developed countries will face an uncertain future．

A．Even you may start to admire his plans．

B．This also reduces government tax income．

C．Why should their motivations be seriously considered?

D．This of course has serious negative effects on their own countries．

E．There should be more job opportunities for highly educated people．
F．So it is important to find out the proper reasons behind the brain drain．
G．Most of the measures taken so far have not reduced the effects of brain drain．