It can be the example of all kinds of sickness
Answer: d
Explanation:
Because it's quick easy and efficient so you can have easy access to it and all you use is your toes and calves.
Crunches
In my educated opinion, crunches would be the best choice out of these options to build strength. A one mile run builds cardio, sit and reach and gymnastics build flexibility and some strength, crunches is strictly abdominal strength.
They permit a production of the large amounts of proteins and enzymes needed for muscle contraction.