2 the second red circle, because the other four days are identified as four questions, then choose one more and one less from the six days, namely C 16 and C 15. Multiplying by A33 is even more wrong, so it is wrong to fix four questions together for four days.
Regarding the need for average grouping, this topic has been changed, because it involves time sequence, so there is no need to divide. If no sequence is involved, averaging is needed. For example, if you want two of six people, one chooses three topics and the other chooses five topics, you need to divide by A22.