Here's why:
* Bascule bridges have a movable section that lifts up to allow boats to pass underneath. London Bridge's movable section is a large, horizontal span that pivots upwards.
* Cable bridges are supported by cables that run from the towers to the deck.
* Suspension bridges are supported by cables that hang down from towers and are connected to the deck.
So, while London Bridge might look like a suspension bridge from a distance, it's actually a bascule bridge!