The correct answer is - the variable.
With the experiment, in the way that Dan had decided to perform it, the fertilizer is the variable, as in one of the parts with strawberries he uses fertilizer, while in the other part he doesn't uses fertilizer.
While this kind of experiment may give Dan some answers, and he might notice differences, still he would have to be more detailed in the experiment to see for sure if the fertilizer is the thing that makes some of the strawberries grow better than the others.
Dan should also put all of the strawberries at places that would receive the same amount of light, experience the same weather conditions, receive the same amount of water, and to be planted in a soil of the same quality. Only like this, after putting the fertilizer, Dan can now if it makes any changes or not.
Cell - neuron, egg, bacteria, perenchyma
tissue - bone
organ - leaf, flower, eye
organ system - blood, human skeleton
organism - mushroom, bear
not 100% sure but tried
The embryo sac which present in egg shell protects it
Sorry I don't know just try to graduate
Away from the sun would be the answer
