我觉得当科学家很难，但是很有意思。

Wǒ juéde dāng kēxuéjiā hěn nán, dànshì hěn yǒuyìsi.

I think being a scientist is hard, but very interesting.

她想当科学家。

Tā xiǎng dāng kēxuéjiā.

She wants to be a scientist.

科学家告诉我们，这个办法很安全。

Kēxuéjiā gàosu wǒmen, zhège bànfǎ hěn ānquán.

The scientist told us that this method is very safe.