Materi 3 sumber: idntimes.com E-k-o-s-i-s-t-e-m = Ekosistem O-r-g-a-n = Organ sumber: health.indozone.id S-u-n-g-a-i = Sungai sumber: detik.com K-o-p-i = Kopi sumber: koffiendo.co.id