Reading Comprehension Success in 20 Minutes a Day, 3rd Edition

1.
Which of the following sentences best summa-
rizes the main idea of the passage?
a.
Express Mail is a good way to send urgent
mail.
b.
Mail service today is more effective and
dependable.
c.
First-class mail usually takes three days or less.
Because 
a
is specific—it tells us 
only
about Express
Mail—it cannot be the main idea. It does not encompass
the rest of the sentences in the paragraph—it doesn’t
cover Priority Mail or first-class mail. Answer 
c
is also
very specific. It tells us only about first class mail, so it,
too, cannot be the main idea.
But 
b
—“Mail service today is more effective and
dependable”—
is
general enough to encompass the
whole passage. And the rest of the sentences 
support
the idea that this sentence asserts: Each sentence offers
“proof ” that the postal service today is indeed more
efficient and reliable. Thus, the writer aims to tell us
about the efficiency and reliability of today’s postal
service.
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F I N D I N G T H E M A I N I D E A
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2 8

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To p i c S e n t e n c e s
You’ll notice that in the paragraph about the postal
service, the main idea is expressed clearly in the first
sentence: “Today’s postal service is more efficient
and reliable than ever before.” A sentence, such as this
one, that clearly expresses the main idea of a para-
graph or passage is often called a 
topic sentence.
In many cases, as in the postal service paragraph,
the topic sentence is at the beginning of the paragraph.
You will also frequently find it at the end. Less often, but
on occasion, the topic sentence may be in the middle of
the passage. Whatever the case, the topic sentence—like
“Today’s postal service is more efficient and reliable
than ever before”—is an assertion, and it needs “proof.”
The proof is found in the facts and ideas that make up
the rest of the passage. (Not all passages provide such
a clear topic sentence that states the main idea. Less
obvious passages will come up in later lessons.)