The essential features of a microarray are:

a. A high density packing of hundreds, to hundreds of millions of targets or probes on a planar surface
b. An imaging system that is programmed to match the coordinates of spotted targets or probes to their corresponding genetic loci
c. A reliance on hybridization of complementary sequences of probes to targets
d. The use of a reporter system such as one or more fluorophores
e. All of the above
f. None of the above