development, disappoint, explode, float, force, harmful, publish, solid, spread, surface, telescope, violent
1. The butterfly _____________ its wings and moved them slowly up and down .
2. That he failed the college entrance examination ______________his parents very much .
3. She found something unusual ____________on the __________of the river, which quite frightened her.
4. The famous writer ____________a lot of popular novels in that ____________firm.
