Chicago! Chicago! That toddler town!

We met Simon's parents in Chicago last week for two fun-filled days and nights in the Windy City! We hit Navy Pier, took an architectural river tour, and ate some great Chicago food.
At Navy Pier!
The gang on their way to the river tour.
Lucy on the boat for the river tour (or "ride" as she referred to it. This is about one second before she fell fast asleep.)
Simon and Erin at the restaurant where Obama announced his candidacy for president. Coincidentally, it's also the restaurant where Lucy threw up maraschino cherries all over the veranda.

What is Lucy laughing at in this video?

Is it:
a. Mommy's funny faces?
b. The fact that Mommy gave her leftover Chinese food and an Activia for dinner?
c. The dog that keeps snorting and/or choking off camera?
d. The excitement of knowing she's flying to Chicago on Wednesday?

Perhaps we'll never know!