Complex sentence: Five events (Men: 3,000 metre Steeplechase, 4 × 400 metre Relay and Octathlon; Women: 10,000 metre and 4 × 100 metre Relay) had only three competitors, and one event (Women's 4 × 400 metre Relay) had only two competitors.
Split into simpler sentences: Five events (Men: 3,000 metre Steeplechase, 4 × 400 metre Relay, and Octathlon; Women: 10,000 metre, and 4 × 100 metre Relay) had only three competitors. One event (Women's 4 × 400 metre Relay) had only two competitors.