Given the task definition and input, reply with output. This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Passage: Both the Shanghai Stock Exchange and the Shenzhen Stock Exchange suspended trading of companies based in southwestern China. Copper rose over speculations that production in southwestern China may be affected, and oil prices dropped over speculations that demand from China would fall. Question: What did the Shanghai Stock Exchange do?
suspended trading