44. Scientists at the Los AlamosNational Laboratory have succeeded for the first time in mining heat from theEarth's interior and producing energy on a commercial scale, enough forefficient generation of electricity and heating factories and homes. A× (A) and producing energy on acommercial scale, enough for efficient generation of electricity and heating 为什么producing不能和mining 平行？ (B) and producing enough energy ona commercial scale for electricity to be generated efficiently and to heat (C) for energy production on acommercial scale, enough for generating electricity efficiently and to heat (D) to produce energy on acommercial scale, enough for generating electricity efficiently and for heating√ (E) to produce enough energy on acommercial scale for efficient generation of electricity and heat
此 题 中为什么producing不能和mining 平行？是一定要用 in producing才对吗？ 什么情况下介词可以省略呢？ | 
