1.Why might a writer include a historical point of reference in an article about a scientific discovery or innovation? (What is the most likely reason?) 1. to help readers distinguish between fact and opinion
2.to help readers recall what they already know about the topic
3. to help readers learn more about history as a subject area
4. to help readers imagine how a complex process works

To help readers recall what they already know about the topic.

Explanation:

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.

awnser:

one thing blogging and good copywriting share is a conversational style, and that means it’s fine to fracture the occasional rule of proper grammar in order to communicate effectively. both bloggers and copywriters routinely end sentences with prepositions, dangle a modifier in a purely technical sense, or make liberal use of the ellipsis when an em dash is the correct choice-all in order to write in the way people actually speak. but there are other mistakes that can detract from your credibility. while we all hope what we have to say is more important than some silly grammatical error, the truth is some people will not subscribe or link to your blog if you make dumb mistakes when you write, and buying from you will be out of the question.