【正确答案】 A

【答案解析】虚拟条件句中的if可以省略，从句的语序要倒装，如：What a great trouble it would be，should the steam，the electric motor，the telegraph and the telephone be removed at a moment's notice!要是瞬间内蒸汽机、马达、电报、电话全部消失，那会造成多么大的麻烦啊！