Task: Question Answering
Input (English): Context: Then I had met another guy who was going to the same university in the flight . So we went around the houston airport for a while , as our ground shuttle was supposed to pick us up at 9:30 pm . The shuttle arrived at the airport around half an hour late . 
Question: Why may the shuttle have been late ?
Output (English): There was very heavy traffic around the airport at the time .