Two explosions near the finish line of the Boston Marathon killed at least 3 people and injured more than 180 others, and currently FBI has figured out how it __________.
7. This year is very special, _______Chinese New Year' s Day falls on Valentine' s Day.
6. How can you call it home? It' s__________a house.
5. When _______about one of the biggest concerns today, many people mention the sharp rise in prices.
4. People begin to know that most environmental problems exist because necessary measures for preventing them _______taken in the past.
3. To write a novel is not as easy as you imagine. It will take a lot of time and_____.