don't I strengthen? don't you strengthen? doesn't she strengthen? don't we strengthen? don't you strengthen? don't they strengthen?
Present continuous
am I not strengthening? aren't you strengthening? isn't she strengthening? aren't we strengthening? aren't you strengthening? aren't they strengthening?
Preterite
didn't I strengthen? didn't you strengthen? didn't she strengthen? didn't we strengthen? didn't you strengthen? didn't they strengthen?
Preterite continuous
wasn't I strengthening? weren't you strengthening? wasn't she strengthening? weren't we strengthening? weren't you strengthening? weren't they strengthening?
Present perfect
haven't I strengthened? haven't you strengthened? hasn't she strengthened? haven't we strengthened? haven't you strengthened? haven't they strengthened?
Present perfect continuous
haven't I been strengthening? haven't you been strengthening? hasn't she been strengthening? haven't we been strengthening? haven't you been strengthening? haven't they been strengthening?
Pluperfect
hadn't I strengthened? hadn't you strengthened? hadn't she strengthened? hadn't we strengthened? hadn't you strengthened? hadn't they strengthened?
Pluperfect continuous
hadn't I been strengthening? hadn't you been strengthening? hadn't she been strengthening? hadn't we been strengthening? hadn't you been strengthening? hadn't they been strengthening?
Future
won't I strengthen? won't you strengthen? won't she strengthen? won't we strengthen? won't you strengthen? won't they strengthen?
Future continuous
won't I be strengthening? won't you be strengthening? won't she be strengthening? won't we be strengthening? won't you be strengthening? won't they be strengthening?
Future perfect
won't I have strengthened? won't you have strengthened? won't she have strengthened? won't we have strengthened? won't you have strengthened? won't they have strengthened?
Future perfect continuous
won't I have been strengthening? won't you have been strengthening? won't she have been strengthening? won't we have been strengthening? won't you have been strengthening? won't they have been strengthening?
Conditional
Present
wouldn't I strengthen? wouldn't you strengthen? wouldn't she strengthen? wouldn't we strengthen? wouldn't you strengthen? wouldn't they strengthen?
Present continuous
wouldn't I be strengthening? wouldn't you be strengthening? wouldn't she be strengthening? wouldn't we be strengthening? wouldn't you be strengthening? wouldn't they be strengthening?
Past
wouldn't I have strengthened? wouldn't you have strengthened? wouldn't she have strengthened? wouldn't we have strengthened? wouldn't you have strengthened? wouldn't they have strengthened?
Past continuous
wouldn't I have been strengthening? wouldn't you have been strengthening? wouldn't she have been strengthening? wouldn't we have been strengthening? wouldn't you have been strengthening? wouldn't they have been strengthening?