The Britich socilogist and activist Barbara Wootton once noted as humorous example of income maldistribution that the elephant that gave rides to childeren at the Whipsnade Zoo was earning annually exactlly what she then earned as director of adult education for London

a, that the elephant that give rides to children at the Whipsnade Zoo was earning

b,that the elephant, giving rides to children at the Whipsnade Zoo, had been earning

c,that there was an elephant giving rides to children at the Whipsnade Zoo, and it earned

d,the elephant that gave rides to children at the Whipsnade Zoo and was earning

e,the elephant giving rides to children at the Whipsnade Zoo and that it earned

OG said that

the structure of "noted... that the elephant, giving rides..., had been earning" implies that the reader already knows about the elephant-that is that the existence of this particular elephant is not new information

I do not understand this explanation. pls, help to explain. Thank you