To find the complement of the event in which Oliver is the first skater in the race, we need to determine all possible orders of the skaters complying with the condition that Naim is the last skater but Oliver is not the first skater.
Given that the skaters must end with Naim, the possible orders can be analyzed as follows:
1. Identify all possible orders without Oliver being the first skater:
- Marco, Oliver, Pedro, Naim
- Marco, Pedro, Oliver, Naim
- Pedro, Marco, Oliver, Naim
- Pedro, Oliver, Marco, Naim
Therefore, the subsets where Oliver is not the first skater and Naim is the last skater are:
1. MOPN
2. MPON
3. PMON
4. POMN
Thus, the subset [tex]\(A\)[/tex] that represents the complement of Oliver being the first skater is:
[tex]\[A = \{\text{MOPN, MPON, PMON, POMN}\}\][/tex]
Hence, the correct answer is:
[tex]\[ A = \{ \text{MOPN, MPON, PMON, POMN} \} \][/tex]