Mechanisation of farming

[ssgmatter]

Although some officials noted that using machines for farming in China costs more than traditional hand cultivation, the mechanization of farming in the village of Long Bow doubled the corn yield while the previous year's costs were cut in half.

(A) mechanization of farming in the village of Long Bow doubled the corn yield while the previous year's costs were cut in half
(B) mechanization of farming in the village of Long Bow doubled the corn yield while cutting costs to half those of the previous year
(C) mechanization of farming in the village of Long Bow doubled the corn yield as cost were cut to half of the previous year's
(D) farming mechanization in the village of Long Bow doubled the corn yield as it cut in half the previous year's costs
(E) farming mechanization in the village of Long Bow doubled the corn yield while costs were cut to half that of the previous year

Please explain why option B and C are wrong/right?.....with reasons

[haveto]

IMO:B

A) "while the previous year’s costs were cut in half " - it doesn't indicate that cost cutting is due to "mechanization of farming ". So wrong.
B) Clearly referring "cutting costs" to "mechanization of farming ". Contender.
C) I don't think "as" can replace "while" here. Moreover, it doesn't indicate that cost reduction is due to mechanization. hence, wrong.
D) "it" ambiguous + wrong "as" - Hence, wrong.
E) "that" is used for plural - it should be "those" - hence, wrong.

Please correct me if I am wrong.
Thank you.