They filmed in the street
I’m guessing it wants you to fill in two major key signatures like D major and C major also with two minor key signatures like A minor and B minor. I picked those key signatures because A minor is the same as C major but it starts on A and D major and B minor is the same but it starts on B
Neurons communicate with each other via electrical events called 'action potentials' and chemical neurotransmitters. At the junction between two neurons (synapse), an action potential causes neuron A to release a chemical neurotransmitter.