Connectors and clauses

[NKB]

By 1918, advances in tractor technology had led to increased yield, efficiency of labor, profit per square acre, and reduced the amount of time in which fields were planted.


A:profit per square acre, and reduced the amount of time

B:profit per square acre, and had reduced the amount of time

C:profit per square acre, and a reduction in the amount of time

D:and profit per square acre, but the amount of time was reduced

E:and profit per square acre while reducing the amount of time


OA : E

Am not able to figure out why D is wrong.
Please explain.

Thanks.
[spoiler][/spoiler]

[pradeepkaushal9518]

here while is required to show the positive side of the advances of tractors.
hence but is used against it

[NKB]

This makes sense.

Another doubt, i was reading the explanation somewhere else:
The reasoning given is below:

This choice correctly separates the "increase" series from the "reduced" series, but adds another error into the sentence. "Increased yield..." is not parallel with "reduced.

Please explain if you can make any sense out of this?

Thanks!

[Yanat]

I feel E is correct.