Here, the desired answer is:partly because certain features are developed in their tomatoes. Unfortunately, the answer choices did not pick it.
First thing needs to be clarified:there is nothing wrong using 'in part', since they are synonymous.
So, guys who think the answer choice D is correct can't ignore A too! For general description, we don't use 'should', unless moral obligation. So, both A and D should be disqualified because of this sublime cause.
In response to B, another thing needs to be clarified. After the verb 'use, here the purpose is clear enough to use infinitive instead of 'for'. Moreover, development is noun;so, it is less preferred. For the same reason, E deserves a surprising attention!
C is awakward and also, not parallel because of...and because...Another blunder in C is distorting the meaning...' partly because of their tomatoes developing certain features'...Tomatoes develop themselves certain features?
D is very tempting. We can say it is a great trap. Even, I fell in. So, don't do SC too fast. Using 'should' kills this option.
So no other better choice except E. Though it hurts parallelism, but it does not hurt as much as other choices. After the verb 'use', because of intention/purpose, we need to use infinitive. The first portion is fine but the second portion(partly because cross-pollination produces results more quickly than does natural selection.) seems not parallel to the first. But, there is no option except this structure, since you can't present the thought here by 'and partyly to produce..'. So, if no other choice to clearly express a thought, you have always that right to bypass parallelism a bit.
So, my answer is E now.