英文翻译：过去的三十年见证了中国经济的迅速发展.The past three decades [have] witnessed china's economy has been developing at an extremely high speed. 不确定那个have要不要加～求解答～

英文翻译：过去的三十年见证了中国经济的迅速发展.The past three decades [have] witnessed china's economy has been developing at an extremely high speed. 不确定那个have要不要加～求解答～
英文翻译：过去的三十年见证了中国经济的迅速发展.
The past three decades [have] witnessed china's economy has been developing at an extremely high speed. 不确定那个have要不要加～求解答～

英文翻译：过去的三十年见证了中国经济的迅速发展.The past three decades [have] witnessed china's economy has been developing at an extremely high speed. 不确定那个have要不要加～求解答～
要的 也可以换成has
过去时是表示过去发生的事情 不加的话表示动作已在过去完成
加上have 现在完成 有延续性 强调对现在的影响
The past three decades 可以看成一个整体 加单三

The past three decades witnessed China's rapid economic development.

The past 30 years is a witness of fast - developing economic of China. 这是另一种方式的翻译，如果你不确定你自己翻译的是否ok，那么我这个也可以。