Final answer:
The correct answer is 'more quickly'.
Step-by-step explanation:
The correct answer to complete the sentence would be A. more quickly. The adjective 'quickly' is the comparative form of 'quick,' so we use 'more' in front of it to indicate a comparison between James and Alex. The options B, C, and D are all incorrect because they use wrong forms of comparison. 'Most quickest' (option B) is redundant, as 'most' and 'quick' both mean the same thing. 'Quickliest' (option C) is not a valid comparative form of the adjective, and 'quicklier' (option D) should be 'more quick' if we want to use the comparative form. Therefore, option A, 'more quickly,' is the correct choice.
Learn more about Comparative forms of adjectives