Early studies of brain tissue that used staining techniques and microscopes from the 19th century described the "nerve net." these early understandings were in error in the sense that the nerve net was believed to be:
a. continuous.
b. composed of discrete individual units.
c. composed of cell bodies, axons, and dendrites.
d. composed of neurotransmitters rather than neurons.

a. continuous

Explanation:

Scientific techniques were significantly different and less sofisticated in the 1800s than the ones we know today. For this reason, there were numerous 'discoveries' that turned out to be incorrect. One of these discoveries was the description of the "nerve net" as scientists thought that it was composed of a single, big continous network of nerve fibers.

This changed when Santiago Ramon y Cajal arrived at the University of Valencia in Spain. He carried out a different experiment: he used thicker parts of tissue and applied a darker stain. With this methodologic improvement, he demonstrated that the brain is actually composed of neurons that are separated by small gaps that are only seen through a microscope.