、。
Are we walking, or taking the bus?
Literal
Walk go [explanatory-の], or-else bus [with-で] go [explanatory-の]?
A casual question using sentence-final の as the question marker (typically with rising intonation: 行くの？). の-ending questions feel softer and more intimate than か-ending ones — often slightly feminine-coded but used by all speakers in close conversation. They often carry an expectation that the listener already knows part of the answer.