relative. But since there is little solid information
on what is the optimal intake of any essential nutrient in
healthy individuals, it would be impossible to give
guidelines that take these proportional needs into the
(17)
account. Just as with other drugs, the relation to
(18)
different vitamin dosages varies, with some people
better able than others to tolerate large amounts. While
we do know that very specifically what the toxic level
(19)
is for vitamin A and D, we are far less sure about
vitamin E, even though it, too, is fat-soluble, and we
still don't understand the water-soluble vitamin, the C
(20)
and the B groups, which the body can't store.

[C]

The telephone system is a circuit-switched network.
For much of the history of the system, when you placed
(21)
a call, you were renting a pair of copper wires that ran
continuously from your telephone to the other party's
phone. You had excluding use of those wires during the
(22)
call; when you hung up, they were rented to someone
else. Today the translation is more complicated. (your call
may well possess a fiber-optic cable or a satellite with
hundreds of other calls), but more conceptually the system
(23)
still works the same way. When you dial the phone, you get
a private connection to one other party.


This is an alternative network architecture called
(24)
packet switching, in which all stations are always connected
to the network, but they receive only the message addressed
to them. It is as if your telephone was always turned in to
(25)
thousands of conversations going on the wire, but you
(26)
heard only the occasional word intended to you. Most
(27)
computer networks employ packet switching, because
it is more efficient than circuit switching when traffic
is heavy. It seems reasonable the existing packet-switched
(28)
network will grow, and new one may be created; they could
(29)
well absorb traffic that would otherwise go to the telephone
system and thereby reduce the need for telephone numbers.
(30)

[D]

The German poet and polymath Johann Wolfgang von Goethe
pondered the question of how organisms develop in his scientific
studies of form and structure immature plants and animals, a field he
found and named morphology. His search for a single basic body plan
(31)
across all life-forms led him to think about the prevalence of repeating
(32)
segments in body structures. The spinal columns of fish, reptiles,
(33)
birds and mammals, for instance, all are made of long strings of
(34)
repeated vertebrae. Among invertebrates the growth of virtually
identical segments is how striking: in earthworms, for example, even
(35)
internal organs are repeated in serial segments. Likewise, the
abdomen of flies and other insects are segmented, as are the
(36)
successive wormlike articulations in crabs, shrimps and other
crustaceans. To Goethe the evidence suggested that nature takes a
building-block approach to generate life, repeating a basic element
(37)
again and again to arrive at a complicated organism. The only glaring
(38)
hole he could see in the theory was the apparent lack of any sort of
segmentation in the vertebrate heads. In 1970 he hypothesized that
(39)
spinal vertebrate is modified during the development to form the
(40)
skull.

[E]

Literature is a means by which we know ourselves. By it we
(41)
meet future selves, and recognize past selves; against it we match our
present self. Its primary function is to validate and re-create the self
in all its individuality and distinctness. In doing so, it cements a
sense of relationship between the self and the otherness of the book,
and allows us a notion of ourselves as sociable. Its shared knowledge
is vicarious experience; by this means we enlarge our understandings
(42)

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