After setting up a PCR reaction Phil noticed that he'd forgotten to put primers into the mix. When he runs a gel of the PCR reaction after the reaction is finished he sees a positive result. Is this result expected

This is an unexpected result. Absence of primers means that DNA polymerase cannot bind with the template DNA and allow its amplification. If Phil sees a positive band, it should be because of contamination of primers (same set of primer or other) with DNTPs, water, MgCl2, or PCR buffer. This is the reason that a negative run for PCR is always recommended.

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.

the answer is "a.) well–developed vascular system."

explanation: