VOA慢速英语:Studying White Roofs as a Way to Reduce Urban Heat

burn off烧掉,蒸发

例句：The farmers are burning off the stubble in the fields.
      农民们正在把田里的麦茬烧掉。

2.Doctor Wilber says catheter ablation is not meant to be the first treatment choice for atrial fibrillation.

is meant to意味着，为了

例句：Where were you meant to is guarding?
      你打算防守哪里？ 

3.One such material is asphalt, a substance often placed on top of buildings and used to cover road surfaces.

on top of在…上边, 在…上方

例句：Put this book on top of the others.
      把这本书放在其他书的上边。

除…之外

例句：He lost his job and on top of that his wife left him.
      他失业了, 不仅如此, 他妻子也离开了他。