6. Statement 1 (S1): If the obligation does not fix a period but from its nature and the circumstances it can inferred that a period was intended the court may fix the duration thereof. Statement 2 (S2): Once the court fixed the period the parties cannot change it anymore.

(A) both statements are true

(B) both are false

(C) only S1 is true

(D) only S2 is true

Brief explanation will do. Thanks!