Step 1: Understanding the Correct Verb Form:
In this sentence, the correct past tense verb "forgot" should be used. "Can't believe" signals that the speaker is talking about something that happened in the past. The correct form here is "forgot," the simple past of "forget."
Step 2: Analyzing the Options:
- I forget: This is the present tense of "forget," which is incorrect because the sentence is referring to a past event.
- I have forget: This is grammatically incorrect because the correct form is "forgotten," but it should also be used with the auxiliary verb "have" in the present perfect tense, which isn't appropriate here.
- I forgotten: This is the past participle of "forget," but it should be used with an auxiliary verb (e.g., "have").
- I forgot: The correct past tense of "forget" in the sentence.
Step 3: Conclusion:
The correct verb form is I forgot.