When ______ about the possibility that Justin was taken by aliens, Detective Sam Peterson said that there was no hard evidence about this.
The English teacherher students how to improve their comprehension skill since last week.
---- Sorry, I have to ______ now. It’s time for class. ---- OK, I’ll call back later.
Before a problem can be solved, it must be obvious ______the problem itself is.
In the global economy, a new drug for cancer, it is discovered, will create many economic possibilities around the world.
Shortly after suffering from a massive earthquake and to ruins, the city took on a new look.