Please answer the question below ...

Please answer the question below ... 134. How many chromosomes will the onion root tip cell have at GI phase, after S-phase and after M•ase, if it 16 chromoson-es in nesophyll cell (1) 16. 32, 32 (3) 8. 16, 16 (2) 16, 32, 16 (4) 16, 16, 16

Dear student,
In G1 phase chromosome number would be 16, after S phase it would be 16 chromosomes, and finally after M-phase it would be 16 chromosomes. 
It is so because replication occurs during S phase of mitosis during which the DNA content doubles, and at the end of Mitosis the chromosomes get separated and are restored. 
Option 4 is correct.

Regards