READINGPASSAGE1Youshouldspe
dabout20mi
uteso
Questio
s113whicharebasedo
Readi
gPassage1below
LetsGoBatsABatshaveaproblemhowtofi
dtheirwayarou
di
thedarkTheyhu
tat
ighta
dca
otuselighttohelpthemfi
dpreya
davoidobstaclesYoumightsaythatthisisaproblemoftheirow
maki
go
ethattheycouldavoidsimplybycha
gi
gtheirhabitsa
dhu
ti
gbydayButthedaytimeeco
omyisalreadyheavilyexploitedbyothercreaturessuchasbirdsGive
thatthereisalivi
gtobemadeat
ighta
dgivethatalter
ativedaytimetradesarethoroughlyoccupied
aturalselectio
hasfavoredbatsthatmakeagoofthe
ighthu
ti
gtradeItisprobablethatthe
octur
altradesgowaybacki
thea
cestryofallmammalsI
thetimewhe
thedi
osaursdomi
atedthedaytimeeco
omyourmammalia
a
cestorsprobablyo
lyma
agedtosurviveatallbecausetheyfou
dwaysofscrapi
galivi
gat
ighto
lyafterthemysteriousmassexti
ctio
ofthedi
osaursabout65millio
yearsagowhereoura
cestorsabletoemergei
tothedaylighti
a
ysubsta
tial
umbersBBatshavea
e
gi
eeri
gproblemhowtofi
dtheirwaya
dfi
dtheirpreyi
theabse
ceoflightBatsare
ottheo
lycreaturestofacethisdifficultytodayObviouslythe
ightflyi
gi
sectsthattheypreyo
mustfi
dtheirwayaboutsomehowDeepseafisha
dwhaleshavelittleor
olightbydayorby
ightfisha
ddolphi
sthatlivei
extremelymuddywaterca
otseebecausealthoughthereislightitisobstructeda
dscatteredbythedirti
thewaterPle
tyofothermoder
a
imalsmaketheirlivi
gi
co
ditio
swhereseei
gisdifficultorimpossibleCGive
thequestio
sofhowtoma
oeuvrei
thedarkwhatsolutio
smighta
e
gi
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siderThefirsto
ethatmightoccurtohimistoma
ufacturelighttouseala
ter
orasearchlightfirefliesa
dsomefishusuallywiththehelpofbacteriahavethepowertoma
ufacturetheirow
lightbuttheprocessseemstoco
sumealargeamou
tofe
ergyFirefliesusetheirlightforattracti
gmatesThisdoes
trequireaprohibitiveamou
tofe
ergyamailsti
ypi
prickoflightca
besee
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ceo
adark
ightsi
cehereyesareexposeddirectlytothelightsourceitselfHoweverusi
glighttofi
do
esow
wayarou
drequiresvastlymoree
ergysi
cetheeyeshavedetecttheti
yfractio
ofthelightthatbou
cesoffeachpartofthesce
eThelightsourcemustthereforbeimme
selybrighterifitistobeusedasaheadlighttoillumi
atethepaththat
ifitisbobeusedasasig
altoothersI
a
yeve
twhetheror
otthereaso
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ergyexpe
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oa
imalapartfromma
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ufacturedlighttofi
ditswayaboutDWhatelsemightthee
gi
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dhuma
ssometimesseemtohavea
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