Tienes que ..... fuerte para el partido de mañana.
B
Correct answer
Explanation
This tests ser vs estar with the adjective 'fuerte' (strong). 'Tienes que estar fuerte' refers to being in a state of strength/condition for the match tomorrow - this is temporary. If it were about personality, it would use 'ser'. 'Eres' and 'eres' are forms of 'ser', which would describe being strong as a permanent trait.