The past participle of the verb "develop" is "developed."
The past participle of the verb "study" is "studied."
visit is a regular verb so the past and the past participle are both verb + ed ievisitedvisited is the past participle of the verb visit.
The past participle of the verb to do is "done."
The past participle of the verb "occur" is "occurred."
With had the past participle of a verb is used is used not the past form.swim swam (past) swum (past participle).I had swum in the race last year.
The past participle of the verb "develop" is "developed."
The past participle of the verb "study" is "studied."
visit is a regular verb so the past and the past participle are both verb + ed ievisitedvisited is the past participle of the verb visit.
The past participle of the verb to do is "done."
The past participle of the verb "occur" is "occurred."
The past participle of the verb "be" is "been."
There is no past participle. The idiomatic construction "have to" means "must" and is used as an auxiliary verb. (The verb to have has the past tense had and the past participle had.)
Invented is the past participle of the verb invent. verb /past /past participle = invent /invented /invented
The past participle of the verb "like" is "liked".
The past participle of the verb to have is had.
"Red" is not a verb and therefore does not have a past participle. The closest verb form is "redden". Its past participle is "reddened"