Questions

A Sound wave needs a medium for propogation. Hence, Sound cannot travel through a vacuum.

A vacuum is an area without any air, like space. So sound cannot travel through space because there is no matter for the vibrations to work in.

Refer National symbols

Continuously rendered services are those services, which are prepared and provided only to the customers who are physically present. This kind of service is not finished in instant time; it is a process, which is extended to a time limit. It is a kind of face-to-face interaction. For example reservation service, restaurant service, massage, etc.

 It can be possible in only B.C. i.e, Before Christ. That was about 2000 years ago.

 Given, 

 In 1990 B.C = 2000 + 1990 = 3990 years ago, a person is 15 years Old  

=> In 1995 B.C = 2000 + 1995 = 3995 years ago, the same person will be 10 years Old 

Therefore, In 2000 B.C = 2000 + 2000 = 4000 years ago, the same person will be 5 years Old.

Aluminium being a good conductor of heat conducts away the heat from the substance quite easily and causes quick freezing.