Multi-choice problem: Continue writing the next sentence in this paragraph:

How to get your legs and butt in shape
Run stairs.
Find a set of stairs that are not too steep and that are 30 or more steps high. Start off by running up one flight of stairs, then walk down one.

Choose from:
a). Then do 10 or 15 steps to jog across the floor faster. Then, next, the run up two stairs you will repeat.
b). For a 30 second run, take 10 steps and then finish the 10 steps moving down to the ground. Sprint to the stairs and then up another (and then down from there! You won't have enough time to rest).
c). Then jump up and down each stair two or three times to get a good feel for how your feet operate. After you learn how to put the muscles in your legs into shape, you can show off your muscles by using them in other exercises.
d). Next, run up two flights and walk down one. Finally, run up three flights and walk down one, completing the circuit.
d).