a tonne of wheat的用法和样例：
- This strain of wheat can grow during a cold spring.
- It is possible to extract more gold out of a tonne of electronic circuitry than from a tonne of gold-bearing rock.
- How much it will cost Fortescue to produce a tonne of ore is the source of much debate in Australia's mining community.
- In industrialised countries the price of a permit to emit a tonne of carbon dioxide will need to reach $50 by 2020 and $110 by 2030.