Ostriches(鸵鸟) have been said to be so stupid that they react to danger by burying their heads in sand. This belief caused the popular phrases to be born: play the ostrich. It’s often used to describe people 小题1:________ refuse to face painful facts. They prefer to ignore the truth. It is like children sticking their fingers in the ears 小题2:________ crying, “I can’t hear you!”

But do ostriches really bury their heads in sand when they are in danger? The answer is no for sure! 小题3:_______ ostriches are flightless(不会飞的) birds, they can run as fast as 40 miles per hour. So, if they find 小题4:_______ in danger, they will run very fast.

It’s a false statement we’ve thought of as 小题5:________ truth for long. So, how did the phrase “play the ostrich” come from? Well,小题6:______ fact, ostriches swallow sand and pebbles(鹅卵石) to help grind(磨碎) food in their stomachs. This means they have to bend 小题7:_______ and put their heads into sand to collect pebbles. That’s 小题8:_______ a false statement was born

防火墙按体系结构可以分为（）、（）、（）和通过混合组合而衍生的其他结构的防火墙。