Several students were working _____the difficult math problem after class. [ ]

In my opinion, he doesn’t seem ___________ to take this job.

The population of the world ____ still ____ now.

In the past few years, so many areas throughout the world have been hit by such destructive earthquakes, snowstorms and tsunamis ________ we have never experienced before, ________ makes us worried a lot about nature disasters.

Must I answer it in English?—No, you _______. You can use Chinese.