Which phrase most accurately describes a chemical
change?
a change on the molecular level
a change in appearance
a change in taste
a change in form

A change in form

Explanation:

A chemical change is a change in form, state, etc

the answer should be monarchy

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).