He Can Alway Bring Pleasure To His Audience While Singing.为什

while 引导的是时间状语从句,当从句的主语和主句的主语一致,且句中含有be时,从句的主语和系词可以一并省略.
因此 He Can Alway Bring Pleasure To His Audience While he is Singing 就等于
He Can Alway Bring Pleasure To His Audience While Singing
同样地,
he worked day and night when (he was) a little boy.
供参考.