jmh530

Yes, only relying on Schweser may work for L1 but after that...

Re the PE-issue: It is positively correlated to the stocks/bonds but not a 1 of course (remember something in the .60ies if I'm correct). Thus, it provides some diversification but in the gray area, where you should choose if f.e. commidities are providing a better diversification, you should choose the latter.

That's how I understand it

Maybe studies have even shown that the return enhancement has a greater impact on overall performance than the diversification part (just guessing!), but IMO CFAI does asks some complicated but not too ambigious questions.