Laredo advertises a reward for the return of his lost dog. Miguel, who does not know of the reward, finds and returns the dog, without asking for reward. Miguel cannot recover the reward, because he:.
a. did not confer a benefit on Laredo by returning the dog.
b. did not know of the reward when he returned the dog.
c. did not ask for the reward when he returned the dog.
d. returned the dog.

B) did not know of the reward when he returned the dog.

Explanation:

Since Miguel didn't know about the reward when he returned the dog, he didn't claim it at that moment. The fact that Laredo offered a reward for his lost dog doesn't mean that the dog couldn't return without the reward being paid. For example, if a police officer returned the dog, then he/she cannot claim the reward.

If Laredo told Miguel about the reward and gave ti to him even without Miguel asking, then Miguel can collect it, but if Laredo doesn't say anything then there is no reward to collect.