The use of "fuller" is incorrect in this sentence, as "fuller" implies a comparison, but is not comparing anything in the sentence. The use of the simple adjective "full" is perfectly appropriate in the sentence, making the correct answer choice "about the full extent of his condition."

Calories can be counted, and so we use the word "fewer." "Less" is for quantities that cannot be counted, such as water.  

As the question compares two people, a comparative form of the adjective in question must be used, meaning that "few," the regular form of the adjective, and "least" and "fewest," which are each superlative forms, are incorrect. While "fewer" and "less" might each look like a potentially correct answer, "fewer" is used to distinguish between countable nouns, while "less" is used to distinguish between uncountable nouns, like "water." (You can tell if a noun is countable or not if you could precede it with a number, and "seven water" doesn't make sense, given how "water" is used here.) So, "less" is the correct answer.

"Intelligently" is an adverb and adverbs are not used comparatively, so we need to change "intelligently" to "intelligent," an adjective. Also, "lesser," an adjective, needs to be changed to a determiner, "less." So, "less intelligent" is the correct answer.

If only two things are being compared, the comparative form ("better," "bigger," "smarter," etc.) is correct. If three or more things are being compared, the superlative form ("best," "biggest," "smartest," etc.) is correct. Because there are only the two brothers here, we use the comparative form: “worse” and not “worst.” In addition, because “worse musician” is more concise than “worse of the two musicians,” it is the better answer.

If only two things are being compared, the comparative form ("better," "bigger," "smarter," etc.) is correct. If three or more things are being compared, the superlative form ("best," "biggest," "smartest," etc.) is correct. Because there are three gardens here, we use the concise superlative form: “prettiest” and not “prettier,” “most pretty,” or “most prettiest.”

When comparing more than two items, you should use superlative adjectives. So, in this case, you should use the word "best."

This sentence contains a superlative adjective error. When forming a superlative in English, the pattern "most + positive form" or "positive form + -est" is used (e.g. "most great" or "greatest"). The word "most" is not mixed with the superlative "____________-est." It is also clear from the context of the sentence that the company thinks that the employees are the best option, not just better than some alternative, so the superlative form is needed, not the comparative forms "greater" or "more great." The correct answer is, "the company believed that its employees were its greatest asset."

This sentence misuses the adjective "great." The form "more greater" does not exist in English. Either "more great" or "greater" would be correct, but the two cannot be mixed. Furthermore, you cannot use the superlative form (e.g. greatest/best) with the word "than." The correct choice is, "Nathan's software is more great than competing software."

This sentence contains an error in the form of the comparative adjective. When forming the comparative form of an adjective, use either the "more + adjective (i.e. more cute)" form or "adjective + -er (i.e. cuter)" form. You cannot mix the two and cannot use any words that indicate a superlative (i.e. most). The correct choice is, "this actress was more cute than all of the others."