Topic: Group verb,

Best Answer Explained in Below-:

The phrase “I could not make out what you said” is an idiomatic expression in English that means the speaker was unable to understand or discern the information being conveyed. The verb "make out" specifically refers to the ability to perceive, comprehend, or identify something that may not be clear or distinct.

In this context, “make out” is commonly used when discussing auditory information that is difficult to comprehend, perhaps due to background noise or unclear speech. It contrasts with the other options, which do not form idiomatic expressions that fit this scenario.

For instance, “make up” typically means to invent or fabricate something, “make of” is often used to inquire about someone’s opinion regarding a situation or object, and “make off” usually implies leaving hastily or escaping. None of these options logically convey the intended meaning of struggling to understand spoken words. Therefore, "make out" is the only choice that accurately expresses the idea of not being able to interpret or grasp what was said.