Answer:
A). Metaphors fail when they have been used so often that readers gain nothing new from them.
Step-by-step explanation:
Metaphors are demonstrated as one of the most commonly employed literary devices that involve an implicit comparison between two distinct things sharing common characteristics. For example, she is the moon(girl and moon are completely distinct from each other but share the common characteristic of bringing light in the darkness).
As per the question, metaphor fails 'when they are employed so often that the readers gain nothing new from them.' Metaphors are primarily employed to offer an implicit or symbolic comparison that not only helps the reader transform their understanding but also artistically provides them 'an intrinsic pleasure and transcend the boundaries of literal meaning.' But if they are used so frequently that readers stop gaining that pleasure, experience, and understanding metaphors fail. Thus, option A is the correct answer.