The correct option is B 50 kilometers
Since, the man rides for 10 km everyday.
Kilometers traveled at the end of the
1st day = 10 km
2nd day = 10 + 10 = 20 km
3rd day = 10 + 10 + 10 = 30 km
4th day = 40 km
5th day = 50 km
So, at the end of 5th day, he'll have traveled for 50 kilometers.