What is the neuron's refractory period? O when Na* channels in the axon hillock open, allowing positive ions to enter the cell.
O a period when a neuron cannot produce another action potential because its potassium channels will not open
O a period when a neuron cannot produce another action potential because its sodium channels will not open

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.

Which type of bond forms between water moleculesstrong bondhydrogen bondcovalent bondpolar bond

What is true of sea slugs in these orders