什么是SI单位？
参考答案：
SI单位是国际单位制单位。
读一读，猜猜看，填空。
One duck has a mouth, two eyes, and two legs.
Two ducks have two mouths, four eyes, and four legs.
1. Three ducks have ____________ mouths, ____________ eyes, and ____________ legs.
2. Four ducks have ____________ mouths, ____________ eyes, and ____________ legs.
英译中：International freight forwarding agent
