In alternative legacies or devises, the choice is presumed to be left to the heir upon whom the obligation to give the legacy or devise may be imposed, or the executor or administrator of the estate if no particular heir is so obliged.
If the heir, legatee or devisee, who may have been given the choice, dies before making it, this right shall pass to the respective heirs.
Once made, the choice is irrevocable.
In the alternative legacies or devises, except as herein provided, the provisions of this Code regulating obligations of the same kind shall be observed, save such modifications as may appear from the intention expressed by the testator. (874a)