The first essential in elephant training is to assign to the animal a single mahout who will be entirely responsible for the job.

essential ^{n. [C] fundamentally necessary element or thing 要素，要点，必需品}

• A knowledge of French is an absolute essential.
• the essentials of English grammar
• food, water, and other essentials
• The first essential in time management is setting clear priorities.^{时间管理的首要要素是设定清晰的优先级。}

assign sb. to sth. ^{指派某人做某事；委派某人担任…}

• The commander decided to assign him to the border patrol. ^{指挥官决定指派他去执行边境巡逻任务。}
• The manager decided to assign to the new project a single lead to avoid confusion.^{经理决定给这个新项目指派一个单独的负责人以避免混乱。}

Elephants like to have one master just as dogs do, and are capable of a considerable degree of personal affection.

just as... do ^{正如…一样}

• It was not forced upon them by the survival competition; they could have caught and lived on prey without using poison, just as the thousands of non-poisonous snakes still do.
• I feel just as you do, Mole; simply dead tired, though not body tired. ^{我的感觉跟你一样，莫尔，简直是累死了，虽然身体并不累。}
• A body does just the same in a dream as he'd do if he was awake. ^{一个人在梦中所做的事情和他醒着时所做的事情是一样的。}

affection ^{n. a feeling of liking for a person or place 感情，柔情，喜爱}

• The elderly cat, despite its grumpy appearance, is capable of a considerable degree of personal affection.^{这只老年猫，尽管看起来脾气暴躁，却能够有相当程度的个人情感。}
• Humans are capable of a considerable degree of personal affection even towards inanimate objects.^{人类即使对无生命的物体也能够有相当程度的个人情感。}
• He has a deep affection for the small town where he grew up. ^{他对他长大的那个小镇有着深厚的感情。}

There are even stories of half-trained elephant calves who have refused to feed and pined to death when by some unavoidable circumstance they have been deprived of their own trainer.

feed ^{v.饲养，喂养，为…提供食物}

• And then, when they were dead, the carnivores, like the sabre-toothed cats and the giant wolves, came out to feed and suffered exactly the same fate. ^vi.进食
• After all, all living creatures live by feeding on something else, … ^{vi.捕食（feed on 以...为食）}
• It tires not, nor does it boast of its power; but belongs to the air, travelling it may be six thousand miles to and from its northern nesting home, feeding its flown young as it flies, … ^vt.喂养
• The sick patient refused to feed until his family arrived.^{这位生病的病人拒绝进食，直到他的家人到来。}

pine ^{v. be very unhappy, esp. because sb. has died or gone away 痛苦，伤心（尤指因生离死别）}

• Six months after he left, she was still pining.
• He seemed to pine for his lost youth. ^{他似乎在怀念他逝去的青春。}
• To pine and sigh. ^{令人憔悴和叹息。}
• Legend says the bird pined to death after its mate flew away forever.^{传说这只鸟在它的伴侣永远飞走后，因思念而死。}

do sth. by mistake / accident ^{by 接原因状语}

• I succeeded by good fortune.
• By mere negligence she had seriously wounded the feelings of Maggie.

Such extreme cases must probably be taken with a grain of salt, but they do underline the general principle that the relationship between elephant and mahout is the key to successful training.

take sth. with a grain of salt ^{需要持保留态度/半信半疑}

• If I were you, I'd take his advice with a grain of salt.
• Most of what he says should be taken with a pinch of salt.
• Any rumors you hear about the merger should be taken with a grain of salt.^{你听到的任何关于合并的谣言都应该持保留态度。}
• His exaggerated stories often have to be taken with a grain of salt.^{他夸大的故事往往需要持保留态度。}

A and B ^{语义相关无冠词}

• the relationship between teacher and student ^师生关系
• the conflict between mother and son ^{母子之间的冲突}
• Primarily, the banker-customer relationship is that of debtor and creditor … 

be / hold the key to … ^{是…的关键}

• Working well as a team is the key to success.
• a discovery that may hold the key to our understanding of the universe
• Patience and consistency are the key to successful training of any pet.^{耐心和一致性是训练任何宠物的关键。}

Such extreme cases must probably be taken with a grain of salt, but they do underline the general principle that the relationship between husband and wife is the key to successful marriage. ^{这种极端的例子虽不可全信，但是却的确突出了这一基本原则：夫妻关系是成功婚姻的关键。}