13. which of the following elements is not a noble gas?
a krypton
bargon
c chlorine
d helium

Chlorine is a halogen, not a noble gas.

The last two groups of the periodic table is named as halogen family and Nobel gas family.

The group 17 is composed of gases collectively called as halogen and it includes the following gases:

The group 18 is composed of elements which are collectively called as Nobel gas and it includes:

The below given table shows the halogen and Nobel gas in the periodic table.

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.