In the following question, out of the four alternatives, select the alternative which best expresses the meaning of the idiom "to foam at the mouth".

Introduction / Context:
This question is about understanding an English idiom. Idioms are expressions whose meanings cannot always be guessed from the individual words. The phrase "to foam at the mouth" may sound literal, but in everyday speech it is used metaphorically. You must select the option that correctly captures its figurative meaning.

Given Data / Assumptions:

• Idiom: "to foam at the mouth".
• Option A: to be very angry.
• Option B: to shout loudly.
• Option C: to get very weak, dizzy.
• Option D: to die of poisoning.
• We assume the context is typical conversational or descriptive English rather than medical description.

Concept / Approach:
Literally, an animal or a person might foam at the mouth due to disease or seizure. However, in idiomatic English, the phrase usually describes someone who is extremely angry or furious, almost as if they have lost control. The image suggests such intense rage that it seems physical. Therefore the correct answer must connect the phrase with extreme anger, not with simple shouting, weakness or death.

Step-by-Step Solution:
Step 1: Recall how the idiom is used in stories and reports. You may read that a fan was "foaming at the mouth" about a referee decision. This does not mean a medical emergency, it means the fan was extremely angry.Step 2: Examine option A, "to be very angry". This perfectly matches the common figurative sense of the idiom.Step 3: Examine option B, "to shout loudly". While very angry people may shout, the idiom focuses on the degree of anger, not just on volume of voice.Step 4: Examine option C, "to get very weak, dizzy". This relates to physical collapse and does not match the usual contexts where this idiom appears.Step 5: Examine option D, "to die of poisoning". That is a literal possible cause of actual foaming, but it is not the figurative idiomatic meaning tested in language exams.

Verification / Alternative check:
Place each option in a sentence. "He was foaming at the mouth when he heard the news" is naturally paraphrased as "He was very angry when he heard the news." Replacing it with "He was shouting loudly" or "He was very weak and dizzy" does not match the emotional reaction usually implied. Thus only option A is accurate.

Why Other Options Are Wrong:
Option B is too narrow and focuses on a possible symptom, not on the intense emotional state. Option C and option D move the meaning towards illness and death, which may occur in real life but are not what this idiom signifies in normal conversation or examination usage. Therefore they are distractors, not correct meanings.

Common Pitfalls:
Many learners confuse literal and figurative meanings, especially with vivid phrases like this one. In exam questions about idioms, you should always ask whether the choices reflect a common figurative use, not only a physical possibility. Remember that idioms such as "hit the ceiling", "see red" and "foam at the mouth" all relate to intense anger.

Final Answer:
The idiom "to foam at the mouth" means to be very angry, so option A is correct.