I believe there are no prepositions in this sentence, here is an example of a few prepositional words:
about
below
excepting
off
toward
above
beneath
for
on
under
across
beside(s)
from
onto
underneath
after
between
in
out
until
against
beyond
in front of
outside
up
along
but
inside
over
upon
among
by
in spite of
past
up to
around
concerning
instead of
regarding
with
at
despite
into
since
within
because of
down
like
through
without
before
during
near
throughout
with regard to
behind
except
of
A public good is a good that doesn't cause rivalry and doesn't exclude anyone and anyone is using it for the good of the society. An examples of a public goods might be fresh air or national security.
what......... are you talking about just log in from a differnt device then