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\*.
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Question: who developed a useful staining method to identify bacteria

Answer: Hans Christian Gram


Question: what is it called when someone always needs attention

Answer: Histrionic personality disorder


Question: when did the apple iphone 4 come out

Answer:
June 24, 2010