Select the phrase/connector from the given three options which can be used to form a single sentence from the two sentences given below, implying the same as expressed in the statement sentence.
Trees are crucial to our long-term survival. They absorb and store the carbon dioxide emissions that cause global heating.
1. When they absorb
2. As they absorb
3. Before the trees
1
Only 1
2
Only 2
3
Only 3
4
Both 1 and 2
5
Both 2 and 3