Eu ___(ir) à praia se _____ (estar) bom tempo. Usa o condicional

Answer: Eu iria à praia se estivesse bom tempo.

Why? You are asked to use the 'condicional', which is, with a few exceptions, combined with the 'conjuntivo'. Whilst the sentence "Eu vou à praia se estiver bom tempo" is also grammatically correct, it would not be answering this particular question.