And of course, highways are at the top of the functional classification system.

当然，高速公路是位于功能分类系统的顶端。

You may notice by now that boulevards aren't in the functional classification system.

您现在可能注意到林荫大道并不属于功能分类系统。

But the traditional functional classification system supports the tree-like road network structure found in the suburbs.

但传统的功能分类体系支持郊区树状的道路网络结构。

Boulevards also predate the functional classification system and are an important part of our urban history.

林荫大道也早于功能分类系统，是我们城市历史的重要组成部分。

While no functional system of this type currently exists, the East Side Tower project in Berlin is set to become the first project in the world to feature this technology when it completes in 2021.

虽然目前还没有这种类型的功能系统，但将于 2021 年完成的柏林东区塔项目将成为世界上第一个采用这种技术的项目。

But if you're fortunate enough to have a fully functional immune system, a cold will probably give you a few relatively mild symptoms. On average, adults catch more than 150 colds throughout their lives.

但是，如果您足够幸运， 拥有功能完备的免疫系统， 那么感冒可能会给您带来一些相对轻微的症状。平均而言，成年人一生中会患上 150 多次感冒。