Do you know the English expression “to hear (something) on the grapevine“? Can you guess the meaning?

William: I heard it on the grapevine that Joe is planning to quit the company.

Claire: Really? When did you hear that?

William: The other day.

Does it mean

a) hear something at a farm which grows grapes

b) hear something while eating grapes

c) hear a lie

d) hear a rumor

The answer is below! ↓

Answer:  d) hear a rumor