The diagram represents a section of undisturbed sedimentary rock. The general location of fossils of several closely related species is indicated. A) B was already extinct when C evolved.
B) C evolved more recently than A, B, and D.
C) D is the ancestor of A, B, and C.
D) A is the ancestor of C and D.

Sydney drew a flow chart to illustrate the nitrogen cycle.which labels best complete the flow chart? x: producers undergo photosynthesis.y: nitrogen compounds are released into the air.x: nitrogen compounds are released into the air.y: producers undergo photosynthesis.x: free nitrogen is in the atmosphere.y: producers absorb nitrogen compounds through their roots.x: producers absorb nitrogen compounds through their roots.y: free nitrogen is in the atmosphere.

The circles, or orbits, for electrons are called energy levels. each level can hold only a certain number of electrons. add electrons to each level until you can't add any more. how many electrons can each level hold?

How does an angiosperm prevent self pollination