Calcium and magnesium dissolved in water are the two most common minerals that make water "hard." The degree of hardness becomes greater as the calcium and magnesium content increases and is related to the concentration of multivalent cations dissolved in the water.
Answer:
I would do a mountain bike personally, its tougher but If you want to do mountain biking then you're going to need something like that. Mountain bikes have great tires and last a long time. Try Dicks sporting goods or any place like that. But if you want a more comfortable bike then I would look into something that allows you to change the gears of the bike.
It can offer protection to the brain, it can collapse under stress, and it can provide attachment sites for teeth.
All of the above are correct
