Swapna, first and foremost, i am taking the initiative to put the spoiler tab for the OA. Please ensure that you use the spoiler tab hereafter.

Now coming to the question:

A.in part that their steers should acquire certain characteristics ['in part' is not parallel to 'partly' used in the other independent clause. Eliminated]

B.in part for the acquisition of certain characteristics in their steers [same error as in A]

C.partly because of their steers acquiring certain characteristics [complete change in meaning. do cattle breeders use cattlebreeding so that their cattle acquires a certain characteristic or that their cattle has acquired a characteristic? Eliminated!]

D.partly because certain characteristics should be acquired by their steers [it is not the passive voice here that is causing a problem but the presence of probability indicator- Should. 'should' is a too strong a word to be used in this context. 'should' implies 100% propbability that it must occur. you cannot say that steers should acquire characteristic. you breed so that they may acquire some characteristic. Eliminated!]

E.partly to acquire certain characteristics in their steers. [bingo! parallelism maintained. meaning in place.]

Hope this helps!

fibbonnaci wrote:
D.partly because certain characteristics should be acquired by their steers [it is not the passive voice here that is causing a problem but the presence of probability indicator- Should. 'should' is a too strong a word to be used in this context. 'should' implies 100% propbability that it must occur. you cannot say that steers should acquire characteristic. you breed so that they may acquire some characteristic. Eliminated!]

E.partly to acquire certain characteristics in their steers. [bingo! parallelism maintained. meaning in place.]

Adding on to that, the sentence uses the term " partly" which certainly indicates that there are couple of other elements that could motivate cattle breeders to use crossbreeding.

As rightly said by "fibbonnaci", "should " should be used in cases where p=1 or 100%.

thanks fibonacci...but the book talks abt passive voice...so u mean to say...there is nothin to do wid voice and its jus because of "should", I felt that anyways the rest of the sentence following the underlined bit is in passive voice

passive voice exists, but you are not eliminating it because of that. 'should' is the main cause of elimination.
Hope this helps