The main idea may appear at any place within each of the five paragraphs that follow.
Write the number of each main idea sentence in the space provided.
1. We all surround ourselves with a "personal bubble" of space, and we go
to great lengths to protect it. We open the bubble to intimates-to our
friends, children, and parents-but we're careful to keep most people out of
this space. ³In a crowded hallway between classes, we might walk with our
books clasped in front of us (a strategy often chosen by females). "When we
stand in line, we make certain there is enough space so that we don't touch
the person in front of us and aren't touched by the person behind us. "At
times, we extend our personal space. In the library, for example, you might
place your coat on the chair next to you-claiming that space for yourself,
even though you aren't using it. If you want to really extend your space,
you might even spread books in front of the other chairs, keeping the whole
table to yourself by giving the impression that others have just stepped
away.
2. 'Fire extended humans' geographical boundaries by allowing them to travel
into regions that were previously too cold to explore. It also kept predators
away, allowing early humans to sleep securely. ³Fire, in fact, has been a
significant factor in human development and progress in many ways. "Other
obvious benefits of fire are its uses in cooking and in hunting. Probably
even more important, however, is that learning to control fire allowed
people to change the very rhythm of their lives. "Before fire, the human daily
cycle coincided with the rising and setting of the sun. "With fire, though,
humans gained time to think and talk about the day's events and to prepare
strategies for coping with tomorrow.
3. 'The stages of life, from birth to death, may seem controlled by biology.
2However, the way we think about life's stages is shaped by society. ³During
the Middle Ages, for example, children dressed-and were expected to
act-just like little adults. Adolescence became a distinct stage of life only
fairly recently, when a separate teenage subculture began to appear. But
in the Middle Ages, young people were "children" until about age 16. Then
they went to work, married, and had their own children. Today, "young
adulthood" has become a new stage of life, stretching from about age 20
to 30. As life expectancy becomes longer and people spend years in active
retirement, older adulthood has also become a distinct life stage.
What number in the paragraph is the main idea sentence?