Final answer:
For the verbs defy and deny, you need to change the y to i before adding the suffix -ed to form defied and denied.
Step-by-step explanation:
For verbs ending in -y preceded by a consonant, you often need to change the y to i before adding the suffix -ed. Given the words delay, defy, deploy, and deny, we must identify which verb follows this rule. In this case, defy becomes defied, and deny becomes denied, because they end in -y preceded by a consonant. In contrast, delay simply becomes delayed and deploy becomes deployed, as they end in -y preceded by a vowel, so the y does not change.