Which of the following would you be least likely to say in response to the question: ¿fuiste a la playa ayer? a. si, y estudié muy bien. c. sí, y jugué en la cancha todo el día. b. sí, y tomé mucho sol. d. sí, y nadé en el mar todo el día.

Generally, if you go to the beach is to have fun and relax, and among those activities that are usually done on the beach, are:

Play on the court all day (jugar en la cancha todo el día), take a lot of sun (tomar mucho sol) and have a wonderful tan, swim in the sea all day (nadar en el mar todo el día), among others.

This means you will not have enough time to study very well while doing all these activities. Therefore, the right answer is:

Si, y estudié muy bien  

Yes, and I studied very well

The other options are incorrect because do not match with the context of activities usually done on the beach.