1. Punctuation: since it is a compound element, no comma is needed.

2. The tiger slept on the large tree branch but kept a watchful eye open.
The tiger slept on the large tree branch, but it kept a watchful eye open.
(compound sentence requires a comma)
The tiger slept on the large tree branch but kept a watchful eye open.
(compound element sentence does not require a comma)
1. The two boys picked blueberries, and they made a pie.

3. s v v The two boys picked blueberries and made a pie.3
s v v
The two boys picked blueberries and made a pie.
(compound element sentence does not require a comma)

4. compound sentence—comma4
compound sentence—comma
S V S
3. The monkeys climbed the trees, and they V
searched for food. 

5. Punctuation: compound element—no comma 5
Punctuation: compound element—no comma
3. The monkeys climbed the trees and searched for food.

6. Punctuation: since these are compound sentences, commas are required.
4. When we left, Lisa closed the curtains, and she turned out the lights.
5. The host greeted us at the door, and the host took our coats. 
6. They were distant relatives, but they were very friendly relatives.

7. 4. When we left, Lisa closed the curtains and turned out the lights.
Punctuation: since these sentences have compound elements, no comma is required.
4. When we left, Lisa closed the curtains and turned out the lights.
5. The host greeted us at the door and took our coats. 
6. They were distant but very friendly relatives.