Надо записать глаголы в времени : think - Put -
Sleep-
Spell-
Teach-
Keep-
Find -
Choouse-

ответ:Thought

Put

Slept

Spelt

Taught

Kept

Found

Chose

Объяснение:

Think-thought-thought
put-put-put
sleep-slept-slept
spell-spelt-spelt
Teach-Taught-Taught
Keep-Kept-Kept
Find-Found-Found
choose-chose-chosen

3 часть это Past Participle