現(xiàn)在進(jìn)行時：
Look!The dinosaur is falling down .
一般過去時：
The dinosaur fell down last night.用（often)改Look!The dinosaur is falling down此句~~often 常用于一般現(xiàn)在時，應(yīng)該這樣改：The dinosaur often falls down.那Yesterdayhedidhomeworkverycarefuly 用（always)和（now)改寫……He always does his homework very carefully.He is doing his homework very carefully now.