Recent studies in bone research indicate that using ultrasound on a broken bone can decrease the healing time by 25% which of these are the most basic levels of organization involved when a bone heals?

Interacting group of various species in a common location. for example, a forest of trees and undergrowth plants, inhabited by animals and rooted in soil containing bacteria and fungi, constitutes a biological community.

Iam not sure but to me it with be a or dsorry if i was late! hope this ! : )if you really want me to find out the answer that is correct tell me and i will do more research but the a or d makes sense to me.