---Do you think yesterday’s math problem was difficult?---Yes. I could work it out.
Stephen Hawking thinks _______ important to have hope in bad situation.
Robert is away. He _______ America since last week.
—Why are you packing so many books? —I’ll _______ to the kids in West China.
My Old Classmate also mentioned some important events that _______ from 1993 to 2013.
—I had a really good weekend at my uncle's. —_______.