Definition: In this task, you are given a news article. Your task is to classify the article to one out of the four topics 'World', 'Sports', 'Business', 'Sci/Tech' if the article's main topic is relevant to the world, sports, business, and science/technology, correspondingly. If you are not sure about the topic, choose the closest option. Note that URLs in the text have been replaced with [Link].
Input: Russia Finds Trace Explosives on 2nd Plane (AP) AP - Russian investigators found explosive residue on the wreckage of the second of two airliners that crashed minutes apart, a security spokesman said Saturday, adding to evidence that terrorists breached security at one of the country's most up-to-date airports.

World