Answer:
Carbon has the greatest ionization energy in that group.
Step-by-step explanation:
I don't know if this is helpful but my teacher used ice cream to explain ionization energy to us. Imagine an ice cream cone standing up straight, ionization energy decreases as you go down, just like how the ice cream cone gets smaller as you go down cause the base of the cone is just a small tip. If you imagine an ice cream cone falling over then it could now be sideways and ionization energy increases from left to right across the periodic table, just like the ice cream cone begins small at the tip and as you go to the right it increases in size.