Answer: The correct sentence is D. Josef walked on the beach, and he also swam in the ocean.
Explanation: D. is the correct sentence because it is the only one who offers a coherent verb tense choice. In other words, D. is the only sentence that conjugates the second verb in the same tense in which the first verb has been conjugated, that is to say the Simple Past Tense. In that way, both verbs ("walked" and "swam") have been conjugated into the Simple Past. In contrast, in the other sentences the verbs do not share the same tense; therefore, they have not been correctly written.
