Final answer:
The disputed use of the word anxious is found in sentence A, where it is used to convey eagerness rather than worry.
Step-by-step explanation:
The disputed use of the word anxious in this English usage guide entry is found in sentence A: Confident in her training and ability, she was anxious to begin the race. Some grammarians argue that anxious should only be used to mean 'worried,' not 'eager.' However, historical usage of anxious to mean 'eager' dates back at least 450 years, which supports the idea that it can be considered a correct meaning. In this sentence, the word anxious is used to indicate eagerness rather than worry.