Proforma
a. 形式上的, 预计的
🗣️ 情景例句
Thanks ... for what?
谢什么？
Troubles never come singly.
祸不单行。
This is because they had no natural enemies until the arrival of humans and therefore did not need to develop flying wings.
这是因为人类到达这里之前，这些鸟没有天敌，因此，它们不需要发育飞行的翅膀。