qa is B

Pests had destroyed grape, celery, chili pepper crops, sugar beet and walnut in the region, but in the 1880s, more effective pest-control methods saved the citrus industry.
A Pests had destroyed grape, celery, chili pepper crops, sugar beet and walnut in the region, but in the 1880s, more effective pest-control methods saved the citrus industry.
B Pests had destroyed grape, celery, chili pepper, sugar beet and walnut crops in the region, but in the 1880s, more effective pest-control methods saved the citrus industry.
C Pests had destroyed grape, celery, chili pepper, sugar beet and walnut crops in the region, but more effective pest-control methods that were introduced in the 1880s saved the citrus industry.
DIn the 1880s, pests destroyed grape, celery, chili pepper, sugar beet and walnut crops in the region and more effective pest-control methods saved the citrus industry.
E In the 1880s, more effective pest-control methods saved the citrus industry from what was destroying grape, celery, chili pepper, sugar beet and walnut crops in the region.

A is out as chilli crops, so out.
B
C methods that, incorrect , AM I CORRECT IN SAYING THAT SHOULD REFER TO NOUN AND NOT VERB, HERE METHODS IS VERB?
D and instead of but,
E focus change, plus what was unclear should be pests