Pick the best preposition to put in the sentence.

1/ This is a _ ./bird/cat/chicken 2/ This is a _ ./cat/chicken/cow 3/ This is a _ ./chicken/cow/dog 4/ This is a _ ./cow/dog/duck 5/ This is a _ ./dog/duck/elephant 6/ This is a _ ./duck/elephant/fish 7/ This is an _ ./elephant/fish/frog 8/ This is a _ ./fish/frog/giraffe 9/ This is a _ ./frog/giraffe/goat 10/ This is a _ ./giraffe/goat/horse 11/ This is a _ ./goat/monkey/mouse 12/ This is a _ ./horse/monkey/mouse 13/ This is a _ ./monkey/mouse/goat 14/ This is a _ ./mouse/goat/monkey 15/ This is a _ ./mouse/sheep/snake 16/ This is a _ ./sheep/snake/tiger 17/ This is a _ ./snake/tiger/bird 18/ This is a _ ./tiger/bird/cat