(2009湖南娄底重点高中联考)             students are required to take part in the boat race．

At first driving requires a lot of concentration, but over time, it just becomes_____.

Although he is old, he’s very          . However, when he was young, he was very lazy.

—How is your recent trip to Sichuan? —I’ve never had ______ one before.

The scientist corresponds with colleagues in order to learn about matters ______ to her own research.