人类的语言能力是经过数千年逐渐演化而来的。

Human language ability has ___evolved gradually over thousands of years.

科学家们认为鱼类在数百万年前进化出了四肢。

Scientists believe that fish ___evolved limbs millions of years ago.

科学家们经过多年研究，终于构想出一套新的实验方法。

After years of research, the scientists ___developed a new experimental method.