<p>APT Travel Agency had paid much <u>attention</u> to complaints that flights booked for customers had been canceled at the last minute by the airline.</p>
<p>The correct answer is <u>(C) attention</u>.</p>
<p>In this sentence, the phrase "paid much ______" is used to describe the level of importance or focus given to the complaints. The word "paid" is a verb and is followed by the noun "attention" in this context. The correct form of the word to fill in the blank is "attention".</p>
<p>Option (A) "attend" is a verb and does not fit the sentence structure. It does not match the noun form needed in the sentence.</p>
<p>Option (B) "attentive" is an adjective and does not fit the sentence structure. It describes a person or their behavior, not the act of paying importance to something.</p>
<p>Option (D) "attending" is a verb form that does not fit the sentence structure. It does not match the noun form needed in the sentence.</p>