प्र: Which action is the best example of a direct observation?

• 1
  listening to a cricket chirp at night and counting the number of chirps per minute
• 2
  determining the seal population of an island by counting seals in 10 square meters of the island
• 3
  identifying which bird was present by the tracks that it leaves in the sand at a beach
• 4
  reading numbers on a heat sensor to conclude that there is a deer in the night woods