外来物种的朋友：外来物种真的造成威胁么？

A Friend to Aliens: Are Invasive Species Really a Big Threat?

youdao

它被建造的主要目的是为了保证国家免于外来入侵的威胁。

Its main purpose was to safeguard the country from external invasion.

youdao

它被建造的主要目的是为了保证国家免于外来入侵的威胁。

Its main purpose was to safeguard the country from external invasion.

youdao