Comes--came
is coughing--was coughing
says--said
doesn't like--didn't like
asks--asked
wants--wanted
has had--had had
asks--asked
takes--took
says--said
doesn't do--didn't do
explains--explained
hasn't come--hadn't come
says--said
walks--walked
has had--had had
understand--understood
has had--had had
Все остальные глаголы не нуждаются в изменении.