In this cloze passage on yoga and exercise, complete the segment “For a runner, it may mean lengthening muscles to gain _______________, while for someone who is hyper-flexible, it could be a way of strengthening core muscles” by choosing the abstract noun that correctly expresses the quality gained by lengthening muscles.

Introduction / Context:
This question is part of a passage that explains how yoga can serve different purposes for different people. In the highlighted line, the author describes what yoga may mean for a runner: “it may mean lengthening muscles to gain _______________.” The missing word must express the abstract quality that results from stretching and lengthening muscles. Such vocabulary based cloze questions test your ability to choose the correct grammatical form and the most natural collocation in context.

Given Data / Assumptions:

• The sentence is: “For a runner, it may mean lengthening muscles to gain _______________, while for someone who is hyper-flexible, it could be a way of strengthening core muscles.”
• Options are: flexible, flexibleness, flexibilities, and flexibility.
• The blank follows the verb “gain,” which typically takes an abstract noun as its object, such as “gain strength,” “gain confidence,” or “gain flexibility.”

Concept / Approach:
The concept here is choosing the correct word form. “Flexible” is an adjective, used to describe a person or thing, not usually something you “gain” directly. “Flexibleness” is technically a noun but is rarely used in modern English. “Flexibilities” is a plural noun and sounds unnatural in this context. The standard abstract noun describing the ability to bend or move easily is “flexibility,” and the common collocation is “gain flexibility.” Therefore the natural and grammatically correct choice is “flexibility.”

Step-by-Step Solution:
Step 1: Identify that the verb before the blank is “gain,” which normally takes a singular abstract noun as its object.Step 2: Recognise that the quality associated with long, stretchable muscles for a runner is the ability to move joints and muscles easily, which is called flexibility.Step 3: Evaluate option D, “flexibility,” which is the standard noun for this quality and fits the phrase “gain flexibility.”Step 4: Note that option A, “flexible,” is an adjective and would require a different structure, such as “to become flexible,” not “to gain flexible.”Step 5: Observe that option B, “flexibleness,” though a noun, is rare and stylistically awkward here.Step 6: See that option C, “flexibilities,” is a plural form that does not suit the general sense of a single quality.Step 7: Conclude that “flexibility” is the only fully appropriate choice.

Verification / Alternative check:
Insert each option into the sentence to test for naturalness. With “flexibility,” the sentence reads: “For a runner, it may mean lengthening muscles to gain flexibility,” which is a common expression in fitness and yoga discussions. In contrast, “gain flexible” is ungrammatical, “gain flexibleness” sounds old fashioned and strange, and “gain flexibilities” suggests multiple types of flexibility, which is not the intended meaning. So both grammatical structure and idiomatic usage confirm “flexibility” as correct.

Why Other Options Are Wrong:
“Flexible” is wrong because it is an adjective and cannot directly follow “gain” in this structure. “Flexibleness” is technically not impossible, but it is rarely used and sounds unnatural in modern English; exam passages generally use standard, frequent forms. “Flexibilities” is incorrect because the context refers to a general quality, not separate categories of flexibility. Therefore none of these alternatives fits both the grammatical and stylistic requirements of the sentence.

Common Pitfalls:
Many learners do not pay attention to the grammatical role required by the verb before the blank. They may choose “flexible” simply because it is familiar, without considering that an adjective cannot serve as the direct object of “gain.” Others may be tempted by unusual forms like “flexibleness” out of uncertainty. To avoid such errors, always identify whether the blank needs a noun, adjective, verb, or adverb, and choose the form that naturally collocates with the surrounding words, especially with common verbs like “gain,” “develop,” or “increase.”

Final Answer:
The correct word to complete the sentence is flexibility, giving “lengthening muscles to gain flexibility.”