A.back
B.up
C.off
D.down

A.took place
B.occurred
C.broke out
D.happened

A.to do
B.and to do
C.and do
D.and doing

A.bare
B.blank
C.hollow
D.empty

A.to look after
B.to be looked after
C.being looked after
D.looking after

A.to some way
B.in the way
C.to some extent
D.in the extent

A.up
B.down
C.through
D.over

A.invented
B.discovered
C.found
D.developed

A.forward
B.off
C.with
D.on

A.take in
B.take out
C.take up
D.take over

A.However
B.Otherwise
C.Nevertheless
D.Moreover