ago for for ago ago for since since for
He
used
to
sing
in
a
choir
twenty
years
They
haven't
seen
each
other
four
years
She
left
university
two
years
He
knew
how
to
speak
Russian
,
but
he
hasn't
spoken
it
at
least
six
years
She
hasn't
done
it
again
it
happened
I
have
lived
here
four
years
now
You
have
studied
English
you
were
at
school
I
told
them
to
be
ready
half
an
hour
I
need
a
break
!
I've
been
working
at
the
computer
3
straight
hour
s