Can you solve the clue?

Somehow you end up in a room which has three doors. Behind the first door, there is deadly poisonous gas. Behind the second door, there are trained assassins with knives. Behind the third door, there are lions which have not eaten in years. Which door would you choose to open?

Now choose:

poisonous gas
Poisonous gas

You are dead

three assassins
Three assassins

You are dead

lions
Lions

You are alive