He has ridden LESS than 140km. He has ridden for 5 hours.
d=vt, distance equals velocity times time.
5s=d
5s=140 but remember he has ridden LESS than 140 km so:
5s<140
The answer is D.
note:
From the above it follows that s<140/5, s<28km/h
s cannot be greater than or equal to 28 because:
5*28=140 and we are told that he rode LESS than 140km.
Just clarifying why 5s>140 is wrong.