It is vital that we _____ act out at once to protect the environment.
We had sat down at the table, when the phone rang.
--- What’s wrong with your car? ----It has a tyre.
---He is fifteen years younger than you.--- ?
Although his experiments were designed to support the ideas the influence of environment upon plants, Mendel found that many characteristics were passed on from one generation to the next.
They are experienced porter(搬运工)who know how to the weight of the rocks they carry.