Because learned patterns of behavior, such as the association of a green light with “go” or the expectation that switches will flip up for “on,” become deeply ingrained, designers should make allowances for that fact, in order not to produce machines that are inefficient or dangerous.

In which one of the following situations is the principle expressed most clearly violated?

Here, we need to look for an answer that reverses the general practice.

(A) Manufacturers have refused to change the standard order of letters on the typewriter keyboard even though some people who have never learned to type find this arrangement of letters bewildering. - Normal notion is not rejected here.

(B) Government regulations require that crucial instruments in airplane cockpits be placed in exactly the same array in all commercial aircraft. - Standard practice again

(C) Automobile manufacturers generally design for all of their automobiles a square or oblong ignition key and a round or oval luggage compartment key. - a standard practice

(D) The only traffic signs that are triangular in shape are “yield” signs. - irrelevant

(E) On some tape recorders the “start” button is red and the “stop” button is yellow. - this reverses the general notion of 'green/yellow is start' and 'red is stop'. This is the correct answer.