[watwut]

To me, ignoring that one and answering questions gives more sense.

According to instructions, the test was judged on completeness. The instructor expected the students to pick set of instructions that make test less complete.

In this variant, answering majority of questions and leaving that one missed is rational behavior.

[ethbr0]

> Make sure you read and follow all instructions.

I'd be worried about someone who receives that instruction, receives an anomalous instruction on the test, and decides to ignore the anomalous instruction.

[cozzyd]

The test was graded on completeness no doubt. Grade = completeness == 0 ? Pass : Fail.