Step 1: Returns in the two cases:
For fractions \(a,b,c\) in A, B, C: rise return \(R=0.1a+5b-2.5c\) and fall return \(F=0.1a-3b+2c\) (in %). The guaranteed return is \(\min(R,F)\).
Step 2: Evaluate each option:
(1) 100% in A: \(R=F=0.1\). Guaranteed 0.1%.
(5) 36% B, 64% C: \(R=1.8-1.6=0.2\), \(F=-1.08+1.28=0.2\). Guaranteed 0.2%.
(3) 64% B, 36% C: \(R=3.2-0.9=2.3\), \(F=-1.92+0.72=-1.2\). Guaranteed \(-1.2\%\).
(4) one third each: \(R\approx0.867\), \(F=-0.3\). Guaranteed \(-0.3\%\).
(2) 30% A, 32% B, 38% C: \(R=0.03+1.6-0.95=0.68\), \(F=0.03-0.96+0.76=-0.17\). Guaranteed \(-0.17\%\).
Step 3: Compare:
The largest guaranteed return is 0.2%, from option (5). This is also the maximum possible (see the previous question), so option (5) is the best strategy.
Final Answer:
The correct option is (5): 36% in option B and 64% in option C.