Well, I'm not a python programmer, and I guessed 14/18 correctly. Some of the questions are hard to know without knowing details of the libraries - JSON, as you point out, for instance (it's also one I got wrong, expecting better throughput). But since each question lists the actual performance numbers after you answer, you can get a feel for how big the overhead is in trivial pure python.

But yeah, some of the questions were poorly chosen. For example, on my machine, using gcc -O2 as the author specifies, the first program always executes instantly, since gcc optmizes that loop to nothing. That leads me to believe he may be running a mac (IIRC those come with absurdly out of date gcc versions as a result of the GPLv3 dispute?) or something else fishy is going on.

One interesting thing to note is that the memory access latency on his machine is almost an order of magnitude faster than you might expect based on "Latency Numbers Every Programmer Should Know" (https://gist.github.com/jboner/2841832) - and that's not a coincidence; those 100ns have always been a bit conservative, and the latency number has slightly improved in the past two decades.