The word with the --er suffixes which is a comparative adjective is A. Faster.
These are adjectives that are used to compare the difference between two or more objects that they modify.
These words are used in sentences where nouns are compared and the --er word 'Faster' is the only word considered to be a comparative adjective in the option, whereas the other words are merely nouns and not comparative adjectives.
The word 'faster' is the comparative form of the word 'fast' and 'fastest' is the superlative form. The other words, Driver, Jumper, and Tester are not in any way comparative adjectives.
Hence, the correct answer is option A.
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