求解一道题 Although the initial setup of generators and a power grid by Edison

Although the initial setup of generators and a power grid by Edison and JP Morgan was rather costly, the electrification of lighting in lower Manhattan doubled work efficiency when the energy costs were cut in half.

• Athe electrification of lighting in lower Manhattan doubled work efficiency when the energy costs were cut in half  
• Bthe electrification of lighting in lower Manhattan doubled work efficiency while cutting energy costs in half  
• Cthe electrification of lighting in lower Manhattan doubled work efficiency while as costs were cut to half
• Dlighting electrification in lower Manhattan doubled work efficiency while energy costs were cut in half  
• Elighting electrification in lower Manhattan doubled work efficiency while costs were cut to half
• 我选的E 感觉 lighting electrification，costs while 前后平行，而且时态也平行 doubled 和 were cut
• 答案选B 是不是while 有什么特殊的用法，请解释下E为什么不好，谢谢