Here's why:
* "Have" is an auxiliary verb used to form perfect tenses (present perfect, past perfect, future perfect).
* "Plus" is a preposition indicating addition.
* "Past participle" is the form of a verb that's used after auxiliary verbs like "have" and "be."
Therefore, the combination "form have plus past participle" doesn't make grammatical sense.
Let's break down the possible structures:
1. "Have + past participle": This forms the present perfect tense, used to express actions completed in the past and related to the present.
* Example: I have eaten breakfast.
2. "Have been + past participle": This forms the present perfect continuous tense, used to express actions that started in the past and continue in the present.
* Example: I have been studying all day.
3. "Form + have + past participle": This is a more complex sentence structure where "form" functions as a noun or verb, followed by a perfect tense.
* Example: The form has been completed.
To understand the grammatical function of "have" and the past participle, you need to examine the specific sentence structure.