Most abundant in bone -
Most abundant protein in bones is collagen. Collagen is formed from glycine proline lysine Proline and lysine are hydroxylated to make OH-proline and OH-lysine. Now, you have to choose between option 2 and 3. As most of the proline in collagen is hydroxyated so best out of these two options is hydroxyproline. Extra information: OH-proline cause extensive hydrogen bonding and hence collagen provide strength to the bones.
Arginine
Hydroxyproline
Proline
Alanine
Proteins bonds and structure