El muchacho sabe (knows) el secreto
muchachas
al
a la
a los
a las
del
de la
de los
de las

de las

Explanation:It translates to the boy knows the secret of ——- girls so it would be the girls or de las

the gravitational force will decrease in strength

explanation:

as objects move farther apart the gravitational ring also does the same and can completely diminish if the objects get far enough apart

there is no "following"