Hi, I wanted to make it so that after killing a creeper only either an iron ingot or a copper ingot would drop out, but sometimes two different ingots drop out at once, how can I fix this?

[
{
"mob": "minecraft:creeper",
"player": true,
"item": "minecraft:iron_ingot",
"itemcount": "0-1"
},
{
"mob": "minecraft:creeper",
"player": true,
"item": "minecraft:copper_ingot",
"itemcount": "0-1"
}
]

Not tested but this might do it:

[
{
"mob": "minecraft:creeper",
"player": true,
"item": ["minecraft:iron_ingot", "minecraft:copper_ingot"],
"itemcount": "1"
}
]

McJty, no, it's not work...