a) The share price {select: +has dramatically fallen; has dramatically been falling}.
b) How long {select: has she worked; +has she been working} in the fashion market?
c) We {select: +have tried; have been trying} to form alliances with several companies before.
d) They {select: have negotiated; +have been negotiating} since August.
e) What {select: have you done; +have you been doing} these days?
f) They {select: +haven't signed; haven't been signing} the agreement yet.
g) Why {select: +has he invested; has he been investing} all his money in this firm?
h) I {select: have installed; +have been installing} a new overhead projector for two hours!