Although you may meet some difficuIties,you should never .
---Do you know about a very popular toy--- the yo-yo(悠悠球)?---Yes. Filipinos(菲律宾人) invented it ________ accident. And it ________ helping kill animals.
To make our city more beautiful, a large number of trees ________ in the mountains last year.
---Our hometown develops so fast.---That’s true. Great changes ________ there in the past few years.
---Mario used to be short, didn’t he?---________. But now he is tall.
---Do you know if we ________ a picnic next week?---I’m not sure. But if it ________ raining, maybe we will.