In the idiom "to fall flat," what does the expression mean?

Introduction / Context:
Idioms such as “to fall flat” are common in everyday English and often appear in examinations on vocabulary and comprehension. They do not usually mean what the words suggest literally. Instead, they have a figurative meaning that must be learned. This question asks you to identify what “to fall flat” means when used about a remark, joke or plan, rather than about a person literally falling down.

Given Data / Assumptions:

• The idiom under consideration is “to fall flat.”
• The options mention flattering, falling in love, having no effect, giving bad news and fainting.
• We assume the idiom is used in contexts like jokes, remarks, speeches or plans.
• The expression is commonly used to describe efforts that do not succeed.
• We need to pick the meaning accepted in standard idiom dictionaries.

Concept / Approach:
When we say that a joke, remark or plan falls flat, we mean it fails to produce the expected reaction. A joke may fall flat if no one laughs. A plan may fall flat if it does not work at all. The idiom can also be extended to performances or speeches that fail to impress the audience. It does not refer to flattering someone, falling in love, delivering bad news or actually falling physically. Therefore, the correct choice is the one that mentions having no effect or failing completely to produce the desired response.

Step-by-Step Solution:
Step 1: Recall that “to fall flat” is often used in sentences like “His joke fell flat” or “The campaign fell flat.”Step 2: Understand that in such sentences, the speaker means the joke did not make anyone laugh or the campaign did not achieve its goals.Step 3: Examine option C: “To have no effect or to fail completely to produce the desired response.” This matches the idiomatic use exactly.Step 4: Examine option A, which refers to flattering someone; there is no connection to the idea of failing or lack of reaction.Step 5: Examine option B, about falling in love; this is entirely unrelated to the idiom.Step 6: Examine option D, giving bad news, and option E, fainting; neither reflects the figurative meaning used in speech about jokes or plans. Thus, option C is the correct interpretation.

Verification / Alternative check:
Consider the sentence, “The comedian's last joke fell flat and the audience stayed silent.” Here, fall flat clearly means the joke failed to make people laugh. Another example: “The company's advertising campaign fell flat, and sales did not increase.” In both cases, the idiom describes a lack of expected response or success. Idiom dictionaries and English usage guides define “fall flat” as “to fail” or “to be ineffective.” None of the other options capture this meaning, so option C is confirmed as correct.

Why Other Options Are Wrong:

• Flattering is about praising someone too much; it has no link to failure or lack of effect.
• Falling in love is an emotional experience and does not relate to jokes or plans failing.
• Giving bad news is an action that can be done successfully; it is unrelated to the idiom “to fall flat.”
• Fainting or collapsing physically is a literal sense of falling, not the figurative, idiomatic sense.

Common Pitfalls:
One pitfall is taking the idiom literally and imagining someone physically falling flat on the ground. Another is choosing an answer that sounds dramatic without checking whether it matches typical usage in example sentences. To avoid such mistakes, remember that idioms often relate to common situations: jokes, performances or plans can “fall flat” when they do not work. Linking the idiom to these contexts makes it easier to recall the correct meaning in exams and real conversations.

Final Answer:
The correct answer is To have no effect or to fail completely to produce the desired response, which is the meaning of the idiom “to fall flat.”