【案例分析题】

Mr Abu，the laboratory attendant，came in from the adjoining store and briskly cleaned the blackboard.He was a retired African sergeant from the Army Medical Corps and was feared by the boys.If he caught any of them in any petty thieving，he offered them the choice of a hard smack on the bottom or of being reported to the science masters.Most boys chose the former as they knew the matter would end there with no long interviews，moral arguments and an entry in the conduct book.
The science master，a man called Vernier，stepped in and stood on his small platform.Vender set the experiments for the day and demonstrated them，then retired behind the ’Church Times’which he read seriously in between walking quickly along the rows of laboratory benches，advising boys.It was a simple heat experiment to show that a dark surface gave out more heat by radiation than a bright surface.
During the class，Vernier was called away to the telephone and Abu as not about，having retired to the lavatory for a smoke.As soon as a posted guard announced that he was out of sight，minor pandemonium （混乱）broke out.Some of the boys raided the store.The wealthier ones took rubber tubing to make catapults and to repair bicycles，and helped themselves to chemicals for developing photographic films.The poorer boys，with a more determined aim，took only things of strict commercial interest which could be sold easily in the market.They emptied stuff into bottles in their pockets.Soda for making soap，magnesium sulphate for opening medicine，salt for cooking，liquid paraffin for women’s hairdressing，and fine yellow iodoform.powder much in demand for sprinkling on sores.Kojo objected mildly to all this.’Oh，shut up!’a few boys said.Sorie，a huge boy who always wore a fez indoors，commanded respect and some leadership in the Class.He was gently drinking his favorite mixture of diluted alcohol and bicarbonate——which he called ’gin and fizz’——from a beaker.’Look here，Kojo，you are getting out of hand.What do you think our parents pay taxes and school fees for？For us to enjoy——or to buy a new ear every year for Simpson？’The other boys laughed.Simpson was the European headmaster，feared by the small boys，adored by the boys in the middle school，and liked，in a critical fashion，with reservations，by some of the senior boys and African masters.He had a passion for new motor-cars，buying one yearly.
’Come to think of it，’Sorie continued to Kojo，’you must take something yourself，then we’ll know we are safe.’’Yes，you must，’the other boys insisted.Kojo gave in and，unwillingly，took a little nitrate for some gunpowder experiments which he was carrying out at home.“Someone!”the look-out called.
The boys ran back to their seats in a moment.Sorie washed out his mouth，at the sink with some water.Mr Abu，the laboratory attendant，entered and observed the innocent expression on the faces of the whole class.He looked round fiercely and suspiciously，and then sniffed the air.It was a physics experiment，but the place smelled chemical.However，Vernier came in then.After asking ff anyone was in difficulties，and finding that no one could in a moment think up anything，he retired to his chair and settled down to an article on Christian reunion.

The boys were afraid of Mr Abu because（）.