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 then which of the following statements are true ?
$(I)$ a high-pressure pulse starts travelling up the pipe, if the other end of the pipe is open
$(II)$ a low -pressure pulse starts travelling up the pipe, if the other end of the pipe is open
$(III)$ a low pressure pulse starts travelling up the pipe, if the other end of the pipe is closed
$(IV)$ a high-pressure pulse starts travelling up the pipe, if the other end of the pipe is closed