سوال ۲ کنکور ارشد مهندسی برق ۱۴۰۵

The sentence needs an adjective that fits the fixed collocation "responsible for" — to be the cause of, or to blame for, something. "The person who built the building is responsible for the current problems" means that person caused (is to blame for) the problems. The other choices do not take "for" in this sense: "leading" (guiding/most important), "different" ("different from"), and "surprising" (unexpected) all leave the sentence ungrammatical or meaningless. So option 4 is correct.