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 did 'open era' began in tennis

SOLUTION: 1968

PROBLEM: who holds priesthood keys in the lds church

SOLUTION: the presidents of the quorums

PROBLEM: who was china fighting in world war 2

SOLUTION:
the Empire of Japan