How many valence electrons does a carbon atom have

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.

What are the two main phases of a cell cycle

As the pea seeds respire, the level of coloured liquid in the left hand part of the capillary tube rises. by referring to what is happening in the apparatus, explain why the level of liquid changes