A synovial joint, also known as a diarthrosis, is the most common and most movable type of joint in a mammal's body. Diarthroses are freely movable articulations. In these joints, the contiguous bony surfaces are covered with articular cartilage and connected by ligaments lined by synovial membrane.
i think it is D, she has already constructed the hypothesis and needs is performing the experiment. there is not much of an observation stage because she is looking at a distant end result in a set time frame.
