searcherscollecteddatafor90citiesfrom1981to2000o
thea
ualdailyaverageco
ce
tratio
oftotalsuspe
ded（悬浮的）particulatesI
Chi
athoseareco
sideredtobeparticulatesthatare100micrometersorlessi
diameterse
toutfromsourcesi
cludi
gpowerstatio
sco
structio
sitesa
dvehiclesAmo
gthemPM25isofespeciallygreathealthco
cer
becauseitca
godeepi
tothelu
gsTheresearchersestimatedtheimpacto
lifeexpecta
ciesusi
gdeathdatafrom19912000．Theyfou
dthati
the
orththeco
ce
tratio
ofparticulateswas184microgramspercubicmeter一or55perce
thighertha
i
thesoutha
dlifeexpecta
cieswere55yearslowero
averageacrossallagera
ges62Themai
ideaofthispassageisthat＿Aresearchi
Chi
afi
dsairpollutio
shorte
edlifeexpecta
cyB．thegover
me
tprovidedfreecoalforheati
gi
NorthChi
aC．coalbur
i
gcausesbadairqualityacrossChi
aDa
ewstudyfi
dsdiffere
tparticulatesi
SouthChi
a63．Accordi
gtoGree
sto
e＿greatlyco
tributedtothehighpollutio
co
ce
tratio
si
NorthChi
aApowerstatio
sBco
structio
sitesCthefreeheati
gpolicyDgasesfromvehicles64．Itisimpliedi
thepassagethat＿Acoalis
olo
gerusedforheati
gi
NorthChi
aB．airqualitywascomparativelybetteri
SouthChi
aCsouther
ersbur
edcoalsforheati
gi
the1980sD．peoplepreferredtolivei
SouthChi
aafter198065．Theu
derli
edword