She won't go to bed until she_____(finish)____(do)her homework.

She won't go to bed until she_____(finish)____(do)her homework.
She won't go to bed until she_____(finish)____(do)her homework.

She won't go to bed until she_____(finish)____(do)her homework.
finishes doing

finishes 因为not...until是直到…才，译为直到她写完作业才能够出去．
并且此句为条件状语从句，所以是主将从现，意思是，主句为将来时，从句为现在时,而She是第三人称单数，所以finish要加es,
doing
finish doing sth 为固定搭配