21. The graphs show the results from an investigation of relative enzymatic activity of four different enzymes in acidic and basic environments. Which enzyme would most likely function well in the stomach?
Pepsin
Papain
Chymotrypsin
Cholinesterase

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.

When does dna replication(make a copy of itself)?

Explain how paleontologists use trilobite fossils as index fossils for various geologic time periods.