E. Fill in the blanks 21. Animals are creation of_____that co-exist with us. 22. Birds have strong_______to flap their wings. 23. Reptiles like crocodiles and turtles can leave on_______and on water. 24. Mammals feed their young with milk produced by their______glands. 25._____are animals with backbones and they are classified into five smaller groups, fishes, amphibians, reptiles, birds and mammals.