prep的一题，求句子的结构是怎样的

qiongle

New equipment and other improvements reduced the amount of time-from eleven hours in 1982 to six in 1988-needed by workers so that they could produce a ton of steel.

• Aneeded by workers so that they could produce
• Bneeded when workers are producing
• Cworkers need in producing
• Dworkers needed to produce
• Eworkers need for their producing of
  

答案D

句子结构是什么？前面已经是完整的一句话了New equipment and other improvements reduced the amount of time；中间没有任何连词吧，后面还能是一句话？workers needed to produce？整个句子结构是怎样的？有点晕啊，没连词就出现两句句子？