The correct answer is option 3: Submarines. This means that the sensitive information that was leaked in August 2016 pertained to the defence platform of submarines.
To better understand the other options:
Option 1: Fifth Generation Fighter Aircraft refers to advanced fighter aircraft that possess stealth capabilities. This option is not the correct answer and is unrelated to the sensitive information leaked in 2016.
Option 2: Combat Helicopters are helicopters specifically designed and equipped for combat missions. Although important in the defense sector, this option is also unrelated to the leaked sensitive information.
Option 4: Unmanned Aerial Vehicles (UAVs) are often referred to as drones and are used for various purposes including reconnaissance and combat. While UAVs play a significant role in defense, they are not the subject of the information leaked in 2016.
Therefore, the correct answer remains option 3: Submarines.