Short answer. No — once only one option is actually possible, you no longer get to choose. Article 1202 provides that when an alternative obligation has several options bound together, but only one prestation is practicable, the debtor loses the right of choice. You must perform whichever option remains genuinely available.
What the law says
The debtor shall lose the right of choice when among the prestations whereby he is alternatively bound, only one is practicable.
Civil Code, Article 1202 — When Only One Prestation Is Practicable. Read the full provision →
What an alternative obligation gives you in the first place
An alternative obligation binds the debtor to render one, and only one, of two or more separate prestations named in the agreement — deliver this car, or that motorcycle, or a stated sum of money, for instance. The right to pick which one to perform ordinarily belongs to the debtor, unless the parties have agreed otherwise. That right of choice is a real, valuable feature of this kind of obligation: it lets the debtor decide, among genuinely available options, which one is most convenient to actually carry out.
The rule when circumstances leave only one option standing
Article 1202 addresses what happens once events overtake that flexibility: the debtor shall lose the right of choice when among the prestations whereby he is alternatively bound, only one is practicable. If two of three alternatives become impossible to perform, for whatever reason, the debtor is no longer picking anything. The single remaining option is simply what must be delivered, because it is the only one left that can actually be carried out.
Why the law removes the choice rather than excusing performance
It might seem generous to say the debtor could instead walk away once most of the options vanish, but Article 1202 does the opposite: it holds the debtor to the one prestation that is still practicable. The logic is straightforward. A choice only means something when there are genuine alternatives to weigh against each other. Once every alternative but one has fallen away, there is nothing left to choose between, and the obligation simply narrows itself down to what remains possible, rather than dissolving altogether or letting the debtor escape performance entirely.
What this means for you in practice
If you owe an alternative obligation and find that all but one of the options has become impossible, whether due to loss of the object, a change in circumstances, or any other cause, you should treat the surviving option as the one you are now bound to perform, not as one among several you may still weigh. Trying to insist on a right to select among options that no longer exist will not hold up under Article 1202. The safer course is to confirm which single prestation remains genuinely practicable and prepare to perform that one, since the law has already made the decision for you at that point.