The boy's grandfather died _ a flood and his grandmother died __old ageA of,from.B from,at.C from,of D of,in选什么.为什么

The boy's grandfather died _ a flood and his grandmother died __old age
A of,from.B from,at.C from,of D of,in
选什么.为什么

C
die from 死于外因
die of 死于内因

C