Plz its urgent
high energy is required for fusion reactions to occur because the nuclei
a. attract each other because they have like charges
b. attract each other because the have unlike charges
c. repel each other because they have unlike charges
d. repel each other because they have like charges

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation:

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"

wher is the rest of the question

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)