*Answer* - on *Reason* Humne "on" isliye use kiya kyunki "bus" ek aisi public vehicle hai jisme hum andar chalte hain ya khade hote hain (matlab, ek open movement space hota hai). English grammar me: "On" ka use large vehicles ke liye hota hai, jisme log freely move kar sakte hain, jaise: bus, train, plane, ship. "In" ka use small vehicles ke liye hota hai, jisme aap confined hote hain, jaise: car, taxi, auto, rickshaw. Example: ✅ I got on the bus. (Kyunki bus me hum chal sakte hain) ✅ I got in the car. (Kyunki car me confined hote hain) Toh yahan "on" isliye use kiya kyunki bus ek large vehicle hai jisme hum freely move kar sakte hain.