6. I'll give you my friend's home address, _________ I can be reached most evenings. 7.
He’s ____ working in Germany as a representative of a Chinese company.
The scientists are now trying to discover what use could be ____ such material.
This tree looks high and strong but ____ its trunk is hollow.
—Smoking is bad for your health. — Yes, I know. But I simply can’t ____.
– Do you know the West Lake in Hangzhou? – Yes, this is the third time that I ____ this beautiful city.