This question is testing PARALLELISM of lists. When you see a list structure (X, Y, and Z), you must make sure all elements are logically and structurally comparable.

Here is the list in the original sentence:
...the years since independence in 1947 have brought:
1. increased literacy,
2. new roads, and
3. have improved farming techniques in the hinterland

We need this to be a list of nouns: 3 things that the years since independence have brought.

(A) and have improved farming techniques in the hinterland
Not parallel - the 3rd list item must be a noun.

(B) and improved farming techniques to the hinterland
Parallel! Note here that "improved" is functioning as a participial modifier to "techniques," not as a past tense verb.

(C) and in the hinterland farming techniques have improved
"in" creates a prepositional phrase - not parallel

(D) and, in the hinterland, farming techniques that are improved
Since the prepositional phrase with "in" is non-essential, the 3rd list item here is "techniques," so this part is parallel. However, If we read it as "the years... have brought... farming techniques that are improved," the meaning is obscured. We need to make clear that these years brought the improvement itself, not that they brought techniques that incidentally happen to be improved.

(E) and farming techniques have been improved in the hinterland
This is a clause, not a noun. Not parallel.

The answer is B.

For more on PARALLELISM with X, Y, and Z lists, see:
https://www.beatthegmat.com/from-the-ea ... tml#813250
https://www.beatthegmat.com/new-york-ci ... tml#715501
https://www.beatthegmat.com/og-2013-sc- ... tml#799032
https://www.beatthegmat.com/a-recent-st ... tml#813145
https://www.beatthegmat.com/good-questi ... tml#699680