The best way to keep our bones strong within the options that were provided would be (B) Preform muscle strengthening exercises regularly.
From these options we can definitely use the "process of elimination". Option (C) would be thrown out immediately, as vitamin D is an absolute necessity for bone health because Vitamin D actually helps absorb the calcium into our system. So we'd definitely want to get a lot of natural Vitamin D by the sun (but remember your sun block!).
Secondly, option (D) would be thrown out, also. You want to consume dairy products because that's where your natural calcium comes from. As previously established, our bones REQUIRE calcium. Without the calcium, our bones will become brittle.
Lastly, option (A) would help mostly your muscles by stretching. Stretching daily is very important to your physical health and your posture and a lot of other benefits but it's not really related to your bone health.
Thus, the only option that would fit would be, option (B). strength training is extremely beneficial to our bones!
