do I stack? do you stack? does he stack? do we stack? do you stack? do they stack?
Present continuous
am I stacking? are you stacking? is he stacking? are we stacking? are you stacking? are they stacking?
Preterite
did I stack? did you stack? did he stack? did we stack? did you stack? did they stack?
Preterite continuous
was I stacking? were you stacking? was he stacking? were we stacking? were you stacking? were they stacking?
Present perfect
have I stacked? have you stacked? has he stacked? have we stacked? have you stacked? have they stacked?
Present perfect continuous
have I been stacking? have you been stacking? has he been stacking? have we been stacking? have you been stacking? have they been stacking?
Pluperfect
had I stacked? had you stacked? had he stacked? had we stacked? had you stacked? had they stacked?
Pluperfect continuous
had I been stacking? had you been stacking? had he been stacking? had we been stacking? had you been stacking? had they been stacking?
Future
will I stack? will you stack? will he stack? will we stack? will you stack? will they stack?
Future continuous
will I be stacking? will you be stacking? will he be stacking? will we be stacking? will you be stacking? will they be stacking?
Future perfect
will I have stacked? will you have stacked? will he have stacked? will we have stacked? will you have stacked? will they have stacked?
Future perfect continuous
will I have been stacking? will you have been stacking? will he have been stacking? will we have been stacking? will you have been stacking? will they have been stacking?
Conditional
Present
would I stack? would you stack? would he stack? would we stack? would you stack? would they stack?
Present continuous
would I be stacking? would you be stacking? would he be stacking? would we be stacking? would you be stacking? would they be stacking?
Past
would I have stacked? would you have stacked? would he have stacked? would we have stacked? would you have stacked? would they have stacked?
Past continuous
would I have been stacking? would you have been stacking? would he have been stacking? would we have been stacking? would you have been stacking? would they have been stacking?