Answer: Er heißt Jens.
Explanation: In this case, we can see the word 'heißen' is referring to someone else by how it ends with 't' in the sentence. Now considering Jens is a masculine name, we would use the masculine 'er' or 'his'. We can rule out the rest of the answers as 'Sie' refers to 'they' or 'she', 'Die Frau' as it refers to 'the woman', and 'das Mädchen' as it refers to 'the girl'.