The response to variability is a resilient instinct. Elastic instinct (also called the conditioned reflex) is an organism formed in the process of life change with conditions and reflection, under certain conditions unrelated stimulus be signals caused by reflections of the unconditioned stimulus. It is not innate, but the reflection of the organism under certain conditions under certain conditions. Conditioned reflex can make animal learning and memory and non-conditional reflex related, but completely different new reflection activity. The formation of conditioned reflex is the formation or connection of the cerebral cortex, which is based on non-conditioned reflex. With conditioned reflex, animals not only reflect things that have direct physiological meaning, but also those that have indirect physiological significance. Elastic instinct can make animals for the changed things to adjust their instinctive behavior, make it easy to adapt to changes in the environment, thus than rigid instinct has more flexibility and purpose, and the body through the conditioning can not before the arrival of the stimulus itself accordingly reaction, make the body more proactive and initiative. Anyway, elastic instinct is higher biological value of variability of external things more advanced way of ordering reaction, is on the rigid instinct, extension, and the synthesis, make rigid instinct has more purposeful and flexibility 2. Leakage of gasoline pipe interface 6. The accounting benefit is bound by the prudent principle. According to the principle of prudence, when there are a variety of accounting methods to choose from an economic business of an enterprise, it should choose a method that neither overestimates nor depreciates the benefits. Enterprises manipulate profits to achieve homogenization of profits, most of which adopt the method of overestimating earnings, and the subjective selection of the period of value-added. As the dental industry is rapidly expanding, the requirement of dentists and staffs has risen tremendously. A dental clinic needs to consider employing more and more candidates to own top quality and efficient patient care. Apart from patient care, there are lots of other needs that have to be handled with professionalism, trust , care. It is because of this belief that some of the most efficient and experienced staffs including dentists are expected in the industry. However, occasionally, the need for extra dentists could be short-term. On the other hand, some dental practices may additionally require a temporary dentist to meet the duties of another.