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\*.

[Q]: how many times have ajax won the european cup
[A]: four


[Q]: how did kurtz die in the heart of darkness
[A]: jungle fever


[Q]: when did significant amounts of oxygen appear in the earths atmosphere
[A]:
541 million years ago