Yes, the correct answer here is: d) so
Thank you Doc V for answering this question in particular and clarifying the fabrication of this rule. Regrettably, it isn't one of Yama's colleagues who mentioned that fabricated information above. That information is mentioned in one of our outside books which thousands of pupils and hundreds of teachers trust. The puzzle is that the sentence above is written correctly in our student book page 32. It says: It is so hot outside …. . I wonder from which source the author(s) of that outside book got that information. What makes me angry is that they explained that information in Arabic and indicated it by mentioning that the correct answer is: 'such'. Unfortunately, so many teachers and too many students would apply that false, fabricated rule in the exam.