About elephants

One mystery about elephants that seems to have been solved is how elephants communicate with each other.Humans have heard

a whole variety of sounds coming from elephants , but these sounds are not the only way that elephants communicate.

 A new explanation about elephant communication is being proposed .Elephants vibrate the air in their trunks and foreheads

The sound that is created during this vibration has an extremely low pitch; the pitch, in fact , is so low that humans cannot hear it.

1 The passage mainly discusses ..........

2  A mystery in line 1 is ........

3  According to the passage , people 

4   It can be inferred from  the passage that the elephant sounds that humans hear are 

5  The word way in line 3 could best be replaced by 

6  Where do elephants vibrate air ?

7  The word pitch in line 6 is closest in meaning to which of the following?

8 Which of the following is NOT true about the extremely low sound created by elephants ?

9 The word rumblings in line 7 is closest in  meaning to 

10  Where in the passage does the author describe the sound that elephants create in their trunks and foreheads