When the human genome was sequenced last year, scientists gained acces

When the human genome was sequenced last year, scientists gained access to the full text of Creation's reference manual: the 3 billion biochemical 'letters' that spell out our tens of thousands of genes and carry the instructions to make all the tissues, organs, hormones, and enzymes in our body.

This is another interesting question, one from which a lot can be learned. From my personal perspective, I know that my understanding of subtle differences between some elements of GMAT SC goes a long way in the error analysis and the choice of the right answer. One of such key issues is the distinction between to+verb vs for+verbing.

An article written by e-gmat concludes that one should opt for to+verb (infinitive) if the intention of the action being modified is explicit, else we should opt for for+verbing, which offers an explanation for the modified action. This was somewhat helpful, but under what circumstances does one know that the purpose is explicit or not? This question lingered in my mind for quite a while until someway somehow I came across a similar distinction made by MGMAT between an infinitive and a verbing in MGMAT SC book. According to MGMAT, we should ascribe intention only to animate nouns and not to inanimate nouns. Just when I thought I have come across a rule of thumb, an exception was introduced by a sentence: Water droplets freeze to form snow. I was bewildered. According to MGMAT the sentence above is acceptable even though there is no intention. I am hoping this wouldn't be tested on the GMAT lol. Although my doubt is not completely cleared, I am better off. At least going forward whenever I see a split between to+verb (an infinitive) and for+verbing, I will check the subject of the verb being modified and confirm if the subject of the verb or doer of the action is inanimate or animate and whether it makes sense for this subject to have an explicit purpose. If the subject inanimate, then surely it can't have an explicit purpose, so we can safely eliminate that option. We are better of opting for for+verbing.

Based on the above, we can, therefore, eliminate A because the subject of the spell and carry is letters and letters is inanimate, so we can eliminate A since letter cannot have an intention although we are tricked with a very nice looking parallelism between the verbs spell and carry. This same reasoning can be extended to eliminate D and B also.

Now we will be left with C and E. Both use for making. At this point, one cannot depend on grammar, at least that's what I think lol. So we need to turn our attention to meaning. As rightly pointed out by many posts, the meaning in D is illogical. So the best answer is E since it is sensical. However, it is worth mentioning that if we use the split between for+verbing and to+verb, we can easily eliminate three options, making our work a bit easier.

Another reason that we can use to eliminate C is that present participles take their tense from the main verb they are linked to in a sentence. In C, the verb to which the verbing carrying and spelling are linked is gained. The verbing modifier denotes present continuous so linking it to a verb that performed an action in the past is problematic and unacceptable. We can eliminate C based on this. Comparing C with E, we notice that the use of a that-clause that spell out our tens of thousands of genes.... in E changed the verb tense to simple present tense spell hence the verbing carrying is in order. Thus E is the right answer.

PS: The purpose of my post is not to provide reasoning to the right answer as the earlier posts by @exc4liber Doer01 and mykrasovski have done an excellent job to narrow down to the right answer, but rather to share my perspectives on the split between for+verbing and to+verb. I won't say I am 100% clear on this distinction yet; the curiosity of my mind is such that I need to understand everything very clearly, and since I'm not at 100% clarity, all additional information, disagreements or otherwise are welcome.

(A) that spell out our tens of thousands of genes and carry the instructions to make

(B) which spell out our tens of thousands of genes, which carry the instructions to make

(C) spelling out our tens of thousands of genes and carrying instructions for making

(D) that spell out our tens of thousands of genes as well as carry the instructions to make

(E) that spell out our tens of thousands of genes carrying the instructions for making