Priority Defined

Whenever a monster is summoned and a trap card that does not negate the summon is activated (such as Trap Hole), if the monster summoned has an ignition effect (such as Snipe Hunter, Dark Armed Dragon, or Chaos Sorcerer), you are allowed to activate as Chain Link 1. For example...

Player 1 Summons Dark Armed Dragon
Player 2 Activates Bottomless Trap Hole
Player 1 Activates Dark Armed Dragon's effect and removes a DARK monster from play.

CHAIN 2 : Bottomless Trap Hole (Speed 2)
CHAIN 1 : Dark Armed Dragon (Speed 1)

Lower Speeds are placed lower on the chain, therefore faster effect have higher priority of activating.

Speed 0
Continuous Effects (not the activation, but the continuation)
(Speed 0 cannot be involved in chains whatsoever and can only be negated by other Speed 0 effects)

Speed 1
Non-Quickplay Spell Cards
Continuous/Ignition/Trigger/Flip Monster Effects

Speed 2
Quick-Play Spell Cards
Normal/Continuous Trap Cards
Quick Monster Effects

Speed 3
Counter Traps

Immediently after Bottomless Trap Hole activates, removing DAD from play, then DAD's effect activates, destroying 1 selected card.