学科网 Did you know that all around the world, 3 to 6 billion trees are cut down each year? Have you ever planted a tree? Z.x.x. K dig vt. & vi. 挖 (洞，沟等 )serious adj. 认真的，严肃的breadfruit n. 面包果reduce vt. & vi. 减少，降低 e.g. We can reduce air pollution by riding bicycle. Zx.xkturn off 关上（开关）e.g. We can save energy by turning off the lights when we leave.recycle vt. 回收利用，循环利用
