Answer:
1 bacterial cell would contain 15N DNA
Step-by-step explanation:
According to conservative model of DNA replication, the two DNA strands do not separate from each other and direct the synthesis of entirely new DNA molecule.
Here, a single bacteria had 15N DNA strands and then it was placed in N14 media. All the subsequent divisions would utilize 14N.
After one division: One 15N DNA and one 14N DNA
After two divisions : One 15N DNA and three 14N DNA
After three divisions: One 15N DNA and seven 14N DNA
Hence only one bacterial cell will contain 15N DNA