Can I give you a call on Sunday?– Sure, but I _______ to the mountains, so call me on my cell phone

For many years, people________ electriccars. However, making them has been more difficult than predicted.

It is the educational system, rather than the teachers, _______ is to blame for the students’ heavy burden nowadays.

It’s ten o’clock. I must go ____.

I want to buy two pens. One is for myself, is for you.