Which factors make studying hadal zone ecosystems difficult?

Ascientific idea becomes valid when it is what?

Select the correct answer. which statement applies only to the axial skeleton, not the appendicular skeleton? a. it contains a pivot joint. b. it has muscles attached that work in pairs. c. it contains red bone marrow. d. it possesses fossa for bone articulation. e. it protects the heart and lungs.

What is the difference between topsoil and clay?