Why is benzene so stable?
Benzene is unusually stable because the electrons in the pi bond are delocalized via resonance. This leads to electron density spread above and below the molecule, stabilizing the benzene ring. This is one of the qualities of aromaticity.
Is the carbon indicated sp, sp2, or sp3 hybridized? H2C*=CH2
The carbon indicated is sp2 hybridized.
How is HT1 activity regulated when mature leaves are isolated from developing leaves and exposed to different concentrations of carbon dioxide?
HT1 activity is regulated in this type of experimental environment by carbon dioxide concentration. This is because an increase in carbon dioxide decreases the activity of HT1 and therefore, the decrease in carbon dioxide increases the activity of HT1.