A person blows into open-end of a long pipe. As a result, a high pressure pulse of air travels down the pipe. When this pulse reaches the other end of the pipe, [2012]
a. a high-pressure pulse starts travelling up the pipe, if the other end of the pipe is open.
b. a low-pressure pulse starts travelling up the pipe, if the other end of the pipe is open.
c. a low-pressure pulse starts travelling up the pipe, if the other end of the pipe is closed.
d. a high-pressure pulse starts travelling up the pipe, if the other end of the pipe is closed.