The city park will be cleaner ___________ people stop dropping litter here and there. 
#56719
A
while
B
if
C
unless
D
before
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 In a position like this, one can ________  stand up _______ lie down . So it is very uncomfortable.
#55361
A
both… and…
B
either… or…
C
neither… nor….
D
not only… but also…