Fill in the gaps with the right forms of verbs in the brackets. Trees (a) — (be) very useful to our life in many ways. We cannot (b) — (live) without their existence. They (c) — (give) us oxygen, and without this oxygen, we cannot (d) — (live) a single moment. They also give us food and fruits which are very beneficial to our health. Besides, we (e) — (get) shade from trees.