Let's fill in the gaps with the correct form of the verbs in Past Perfect tense. Past Perfect is formed using 'had' + past participle (3rd form of the verb).
Before Ken ran to Kerry's house, he had phoned him.
Explanation: The action of phoning happened before Ken ran to Kerry's house.
By the time the show began, all friends had arrived.
Explanation: The friends arrived before the show began.
It had rained for three weeks, so the land was wet.
Explanation: The rain happened for three weeks before the land became wet.