N3 — outside your level filter
by contrast; in response to that — takes the previous sentence as what this one answers to
去年の応募者は百人ほどだった。それに対して、今年は三百人を超えた。
kyonen no oubosha wa hyakunin hodo datta. sore ni taishite, kotoshi wa sanbyakunin o koeta.
Last year's applicants numbered about a hundred. This year, by contrast, the figure passed three hundred. neutral
野党は詳しい説明を求めた。それに対し、大臣は問題はないと述べた。
yatou wa kuwashii setsumei o motometa. sore ni taishi, daijin wa mondai wa nai to nobeta.
The opposition demanded a detailed explanation. In response, the minister said that there was no problem. neutral
Variants
それに対しsorenitaishiformal
drops the て for written register — reports, papers and notices; in speech the full それに対して is the natural one.
それに対して
それにたいしてsore ni taishiteN3formal