The correct answer is canté. However, since "canté" is not one of the options listed, it seems we should choose a form of the verb that fits in the context provided. The sentence "Yo _________ en un concierto en el verano" translates to "I _________ at a concert in the summer."
Among the available options, the most appropriate choice for filling the blank correctly (assuming the sentence refers to a past action) would be:
cantaré (I will sing)
So, the complete sentence would be: "Yo cantaré en un concierto en el verano."
If you need to pick from the options you've given, then use cantaré.