I think the answer is 90%. According to the recent National institute of Health, Microbes in the human body estimates that 90% of the cells in human body are bacterial, fungal, or otherwise non-human. Despite the arguments that bacteria enjoys a commensal relationship with the humans hosts, only a fraction of the human microbia has been characterized.
Your answer here is Commensalism by process of elimination
The tennis ball. Because of less mass
Axons with large diameters conduct impulse faster than those with small diameters. Also Myelinated axons conduct impulse faster than unmyelinated axons. Axons with the largest diameter are all myelinated, therefore they are capable of salatory conduction (Impulses jump from one myelinated node to another). The smallest diameter axons are unmyelinated, so their conduction is continuous.
I hope this helps. :) :)
