<p>The <u>reluctance</u> of many businesses to invest in online marketing may restrict their scope for growth in the future.</p>
<p>The word "reluctance" is a noun that refers to the state of being unwilling or hesitant to do something. In this sentence, it is used to describe the unwillingness or hesitation of many businesses to invest in online marketing. </p><p>The adjective "reluctant" (option A) describes a person or entity that is unwilling or hesitant, but it is not the correct choice in this sentence because we need a noun to fit grammatically. </p><p>Option B, "reluctantly," is an adverb that describes the manner in which an action is done. It does not fit in the sentence because we are not describing how the businesses invest, but rather the state of their unwillingness to invest. </p><p>Option D, "more reluctant," is a comparative form of the adjective "reluctant" and is not needed in this sentence. </p><p>Therefore, the correct answer is option C, "reluctance," which is the noun form that best fits the sentence.</p>