A stabbing inside a Metro station in the city’s southwest borough has led to the arrests of four youths, Montreal police said Friday.A 35-year-old man was attacked around 8:30 p.m. Thursday inside the Lionel-Groulx station, according to police.The victim suffered serious injuries but his condition was considered stable when he was taken to hospital.Three teenage boys, aged 13, 15 and 17, were arrested, along with an 18-year-old adult. The three minors will appear in court later Friday, while the 18-year-old will do so at a later date.Police are trying to determine the motive behind the attack.An investigation is underway.