BillyBoy,
Since B is not in that group, D is not going to work. You can only give one answer, so then that leaves E by default.
5.4.2.6 b. [For pipe materials with a specified minimum yield strength greater than or equal to 65,000 psi (448 MPa), a change in the AWS classification of the filler metal (see 5.4.2.2)] raises the issue of base material being an essential variable,5.4.2.2 [c. For materials with a specified minimum yield strength greater than or equal to 65,000 psi (448 MPa), each grade shall receive a separate qualification test].
It is my understanding that the practice questions are drawn from previous tests. All test questions are designed to (confuse?) make you think and ferret out the most correct answer.
I've taken the CWI exam 3 times (and passed BTW), and each time walked out of the test site wondering "Did I pass or not????". Never bothered to challenge any questions, because you do not fail by one wrong answer... you fail by one too many wrong answers.
After passing test #2, I was given the task of training other inspectors to prepare for the exam and create my own sample test questions. Not an easy job. My sympathy goes out to the test authors. What might seem a cut and dry simple "that's gotta be the right answer!", when subjected to scrutiny, one misused/poor choice of word can throw a totally different interpretation to the intended question and answer.
Good luck on the exam, and get used to confusion on interpretation of Codes and Specs. This will be your new career. Sometimes you'll be right, sometimes wrong, and sometimes leave the rest of the room scratching their heads... that's when you really feel all warm and fuzzy, and sense of purpose.