What is the particle that is labeled with a question mark (?) in the diagram?

Can someone me with 3 and 4 plz. this is for masteries test.

We are hoping to create 5.72 grams of glucose. the plant was given 4.75 liters of co2 and 2.81 g of h20. which reactant was the limiting reagent? how much excess mass did we have of the other reactant?

List and describe the neurological effects of the vocs and other air pollutants,as described by dr.theo colborn