The problem with this sentence is that it does not use parallel structure. The two things that the system is responsible for should be formatted in the same way: either both should be nouns or both should be "-ing" verbs. Every answer choice mixes up the format of one or the other element, but the correct answer is the only one that formats them in the same way.

The original text contains a faulty comparison. It compares the price of soybeans to corn itself, rather than comparing the price of soybeans to the price of corn. 

Only answer choices "is currently greater than the price of corn" and "has been currently greater than the price of corn" draw the comparison correctly, but answer chioice "has been currently greater than the price of corn" contains a tense error. Since the sentence includes the word "currently," we know we should use present tense. Therefore, answer choice "is currently greater than the price of corn" is correct.

The sentence must have proper parallel structure, which means that all of the items listed must be the same type of word. The first two words in the list are verbs ("froze" and "turned pale"), so the last item in the list should also begin with a verb. So, the pronoun "she" should be removed so that "couldn't say," a past tense verb, matches the other items in the list. The simplest and most concise wording is correct.  

The use of "both...and" in the sentence indicates that the two verb forms are actually contrasted in the sentence and should not be parallel. Therefore, the verb in the underlined portion should indicate either what is taking place now or will take place in the future. "And where it is going," is the correct answer choice.

The pairing of the two phrases indicate that they need to have a parrallel  tense for each verb. Only two answer choices, "to play with toys and to run in parks," and "playing with toys, running in parks," are parrallel, and "playing with toys, running in parks," should be separated by a conjunction.

The rule of parallel structure tells us that the sentence should be consistent in its pattern. Because the sentence refers to “all first aid kits,” all of the nouns—"bandages," "alcohol swabs," "pain relievers," and "an ointment"—should be plural. "An ointment" is the only noun in the list that isn't plural, so replacing it with "ointments" fixes the sentences error.

The tense of all verbs must be parallel, and since the given verb “drinking” is a present participle, the only appropriate options are “watching” and “planning.”

You can therefore eliminate options in which "watch" and "plan" don't agree with each other, as well as options in which those verbs don't agree with "drinking." You are left only with "My mother begins each day by drinking coffee, watching the news, and planning the rest of her day," which is the correct answer.

One cannot compare “works” to “painters.”  One must compare the works of Degas to those of other painters.

The last phrase of the sentence is confusing, as it is unclear exactly who is becoming "a truly great artist." The sentence is best served by making it clear who can become the "truly great artist." The answer choice that best fixes the issue is "Artistic ability is an inborn skill, but always needs to be developed for someone to become a truly great artist."

The problem with the end of the sentence is that the underlined phrase has an unclear reference. "They could as young" does not have an obvious comparison being made. The answer choice "they could when they were young," is the best improvement on the sentence.