I saw a boy fall off the bike and hurt himself.还是I saw a boy

I saw a boy fall off the bike and hurt himself.还是I saw a boy I saw a boy fall off a bike,这句话saw用了过去式,为什么fall不用? i saw a boy ()into the river.用fall还是falling? l saw a little boy fall into the water.是用fall还是falling? 1.The boy fell off his bike and hurt himself b____ I saw a boy _____this cat in the street and he didn't want t i saw a boy.the boy was playing with a cat. i saw a boy crying when i passed the park（后面一个i能去掉吗? i saw a saw saw a saw. suddenly i saw a boy came__(跑)towards me. I saw a boy __in the street this morning ,so I went to ask w I saw a little boy trying when i passed the park,some time l