Animals Can Sense Natural Disasters
Among the dead in South Asia’ s tsunami（海啸）were many tourists at Sri Lanka’ s national wildlife park at Yala. But very few of the park’s animals — elephants, buffaloes, monkeys and wild cats — appear to have died. There are theories that animals can sense natural disasters and run away to safety.
First, it’s possible that the animals may have heard the quake before the tsunami hit. The underwater burst produced sound waves known as infrasound（次声）. Humans can’t hear infrasound, but many animals including dogs, elephants, tigers and pigeons can.
A second early warning sign the animals might have sensed is ground vibration（震动）. The great quake would have produced vibrational waves known as Rayleigh waves. These vibrations move through the ground like waves moving on the surface of the ocean but faster. They travel at ten times the speed of sound. The Rayleigh waves would have reached Sri Lanka hours before the water hit. Mammals, birds, insects and spiders can sense Rayleigh waves. So the animals at Yala might have felt the Rayleigh waves and then run to higher ground.
But what about humans? While we can’t hear infrasound, we can feel it, although we don’t necessarily know we’re feeling it. We also experience Rayleigh waves by special sensors in our joints（关节）, which exist just for that purpose. Sadly, it seems we don’t pay attention to the information when we get it. Maybe we screen it out because there’s so much going on before our eyes and in our ears.
Why did few animals at Yala die when the tsunamis that caused a huge number of human deaths hit?

A．Because human beings cannot hear the infrasonic sound.

B．Because the animals were staying at a higher place in the park.

C．Because the animals were able to run much faster than human beings.

D．Because the animals might have picked up the danger signals and ran away.

Which of the statements about “Rayleigh waves” is true?

A．Rayleigh waves can be felt both by animals and human beings.

B．Rayleigh waves, just like infrasonic sound, can only be felt by animals.

C．Rayleigh waves are vibrational waves that usually cause quakes or tsunamis.

D．Rayleigh waves move on the ocean surface at a speed ten times that of sound waves.

According to the passage, which of the statement is true?

A．We can’t feel the infrasound so we can’t be informed of the danger.

B．We ignore the information of tsunami’s coming even though we can also get it.

C．We were so busy on our minds that we feel neither infrasound nor Rayleigh waves.

D．We can feel Rayleigh waves and infrasound so we can escape the danger like animals.