认真阅读下列短文,根据所读内容在文章后表格中填入恰当的单词。
注意:表格中的每个空格只填1个词。
Searching for the truth
Collecting mid writing news is like researching in history:the best information comes from
those who were there at the time.So if we want to study the history of China in the sixth century
AD,we look at the writings of the people who lived then.They are called the primary sources
because they tell us what it was like to live then.People at a much later date who write about
the same events are called the secondary sources.For example,when we read the original writings
of Jia Sixie on agriculture,we are reading a primary source;when we read about Jia Sixie in our
textbook we are reading secondary source because the passage was written about him and his ideas
many years after he died.
When we make news we use primary and secondary sources.We can see this most clearly in
TV programmes.As we watch the news on TV,the person presenting the programme in the studio
is the secondary source (because he tells us about the news)and the reporter in Iraq or Washington
is the primary source(because he is telling us about what is actually happening there).Without these
reporters acting as primary sources,you would never find out what really happened in a war,earthquake,
sports meeting,concertor festival.These reporters explain what is happening so we have a clearer
idea of what is going on there.They often take photographers with them who act as primary source
by giving pictures of events.
In a newspaper the position is different because these two roles are often combined.This means
a reporter who investigates a story may be the same person who writes it.If this happens,the reporter
is both the primary and the secondary source.But the photographer who works with him/her is still
a primary source.
One of the reasons that it is important to separate primary and secondary sources is that they
help us to decide what is a fact and what is an opinion.A fact is something that everybody agrees
has happened.An opinion is somebody's idea of what happened.So facts and opinions are often
mixed in any report,whether in a newspaper or on TV.
Searching for the truth
=R+2M中，已知R和M的摩尔质量之比为22∶9，当1.6 g X和Y完全反应后，生成4.4 g R。则在此反应中Y和M的质量之比为（ ）