Closely enough related to number of basic operations though I'd say. I'll agree with you if it really just is a multiple choice question without context, but the initial poster did not present it that way, but said that explanation/discussion matters. And then your objections are a good starting point for that.

The worst thing you realistically can do to stall your CPU is miss cache every time you read data from RAM. If you do this for every instruction (which would be quite a feat in itself), you divide your instruction throughput by about 200. But even then, and even on the shittiest modern CPU you'll be retiring millions of instructions per second.

The MSP430, released in 2010, can be clocked down to 32kHz. That's pretty much the state of the art in modern, low-power devices.

And if you know that, I'm pretty sure you'd pass that interview.