The question isn't about three instructions being executed by three separate OS threads. It's about three instructions being executed at the same time on a single thread on a single core.
The interrupt context will only contain a single program counter value; which of the instructions that could currently be considered to be executing on that thread will it actually point to?
The interrupt context will only contain a single program counter value; which of the instructions that could currently be considered to be executing on that thread will it actually point to?