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