Chapter 12, Exercise #8, Rebecca

a) They're my brothers' keepers.
The form of they're that is used shows that the subject is people (brothers' keepers), rather than a statement (there). The use of apostrophe after brothers' shows that there are multiple brothers and the keepers pertain to these multiple brothers. If it were only one brother it would be brother's keepers.
b) He said, "He will take the garbage out."
In this statement the quotation marks show that the speaker is talking about someone else who then becomes the subject of the statement. In the spoken form there would be no quotation marks and the second he pronoun would be vague. It could be he, the speaker, or he, another subject.
c)The red book was read.
In spoken form red/read sound the same and could be interchanged in both cases in this sentence. The written form distinguishes that the red (color) book was read (action).
d) The flower was on the table.
The spelling of flower helps us to discern which type of flower we are talking about. In spoken form, this sentence could refer to either flower or flour because both are pronounced the same.