Choose is an irregular verb, with chose as the past form and chosen as the past participle form.
Examples:
Last week I chose my classes for next semester, but I haven't yet chosen a major. It's hard to choose between podiatry and penology.
Practice:
(a) Fate chooses our relatives, but we _____ our friends.
(b) Last year, she _____ to ignore me, but now I have _____ to ignore her.
