TASK DEFINITION: In this task, You are given an open-domain question that can be answered based on factual information. Your task is to provide \*short\* answer (in a few words only) for the given question. The short answer can be one or more entities or it can also be boolean \*yes\* or \*no\*.
PROBLEM: when were air brakes first used on trucks

SOLUTION: the early 20th century

PROBLEM: how many divisions are there in minor league baseball

SOLUTION: five

PROBLEM: what is the top sport in the usa

SOLUTION:
American football