i am interested in b arch but there is no option for this field in your app. what should be my rank if i score 175 marks in jeemain paper 2

According to previous years data, generally speaking around 220 marks fetched rank of nearly 9200, and upto that rank there's no chance to get admission to NIT and top institutes for B.ARCH., since there closing ranks are somehow between 4k to 6k every year.

AT marks of 175 your rank will be near 14 to 15k.
Still there are lots of colleges to choose from :-) apart from top institutes.
Thank you and best wishes for you.