The second question is wrong!
The explanation is as follows: The total number of grouping cases is C (5, 10)/2! !
The total number of people who are not in a group is c (4 4,8)! ! ! If A is the strongest pair, A will choose four of the other eight as a group, and the rest as a group, without scoring. Ha ha.
The probability is c (4,8)/(c (5, 10)/2) = 5/9.
Other space can only be 4/9.
It's ok to calculate, first AB, then C (3 3,8).
C(3，8)/(C(5， 10)/2)=4/9