Final answer:
The past simple tense of 'shrink' is 'shrank', and the past participle form is 'shrunk'. These are irregular verb forms that deviate from the standard -ed ending in English.
Step-by-step explanation:
The correct verb forms for the word shrink in both the past simple tense and past participle are important to know. The past simple tense formed is 'shrank' while the past participle form is 'shrunk'. These forms are part of the irregular verbs in the English language that do not follow the typical pattern of adding -ed to form the past tense. Instead, they undergo a vowel shift or have unique forms.