If a post synaptic cell is stimulated to threshold by temporal summation this implies that a presynaptic neuron is sending frequent epsp the presynaptic neuron is sending frequent ipsp the postsynaptic cell is sending frequent action potential the postsynaptic cell can be influenced by only one presynaptic cell

The answer is presynaptic neuron is sending frequent epsp (excitatory postsynaptic potential). This temporary depolarization of postsynaptic membrane potential is caused by the flow of positively charged ions into the postsynaptic cell, as a result of opening ligand-gated ion channels. Accumulation of these EPSPs add up to the threshold of the post-synaptic neurons’ threshold to fire. The attached picture illustrates this.

answer; ///(b) it is composed of four protein chains and four heme groups;