In response to

के जवाब में

English Usage: He wrote a letter in reply to her request.

Hindi Usage: उसने उसके अनुरोध के उत्तर में एक पत्र लिखा।

Refers to a location or direction towards the northern part of a specified area

उत्तर दिशा में

English Usage: The mountains are in the north.

Hindi Usage: पर्वत उत्तर में हैं।

In response; as a reply.

उत्तर में

English Usage: He spoke in reply to her question.

Hindi Usage: उसने उसके प्रश्न के उत्तर में बात की।