Choose the correct tense

Choose the correct tense (simple past or past perfect simple).

1. We __________(give) away the flowers that we__________(pick) 

2. Wendy __________(send) the letter that she wrotehad written.

3. The gardener __________(water)  the trees that he__________(plant)

4. I __________(get) into the/ taxi that my friend__________(call) for me.