The WIT and WIT Workbooks (including the questions and answers) are rife with errors -- especially the older ones.  Even the most recent WIT has quite a few errors...

Plus, some of the information in the earlier 1999 WIT is obsolete and\or no longer covered in the later edition of the WIT.  For example, the rounding of numbers convention has changed and significant figures are not covered in the most recent WIT text.

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The correct answer -- using AWS' more recent rounding convention -- is 28,700 psi (which isn't in the list of answers to the question; 28,717 psi rounded to 3 significant digits).

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Theoretically, the exam can ask a question on any topic -- drawn from any of the sources listed in the Body of Knowledge (both required and suggested readings).

Practically, however, on Part A I think they keep things mostly basic.  So, if you learn what is in the WIT you should pass Part A.  You should learn the diagrams\photos - two notable ones are welding processes and discontinuity radiographs - to the extent that you can identify the process and the type of discontinuity from the diagrams\photos alone.

I would make sure that you understand scientific notation and how to perform calculations.  It's important enough that it is covered in both the WIT book and the on-line training.  You might have a question or two that require you to make conversions using scientific notation or answers that are given in scientific notation only or given in non-scientific notation only.