The correct option is B P
NAD, FMN and ATP molecules acts as co-enzymes, which will get oxidised by accepting electrons from substrates. NAD has 2 molecules of phosphate, ATP has 3 molecules of phosphate and FMN has one phosphate in position 5. So P is common in NAD, ATP and FMN. Thus, option B is correct. Zn, Ca and Mg are not common in ATP, FMN and NAD. Thus, other options are wrong.