In the basic queuing model (M/M/1) , service times are described by

A) binomial probability distributions.
B) negative exponential probability distributions.
C) Poisson probability distributions.
D) normal probability distributions.
E) lognormal distributions.

In the basic queuing model (M/M/1), service times are assumed to follow a negative exponential probability distribution. This means that the time between arrivals and the time spent in service follow an exponential distribution, which is a common assumption in queuing theory. The other distributions listed (binomial, Poisson, normal, and lognormal) are not typically used to model service times in this context.