I have installed windows 7 on my Macbook pro 13 but now how can i open my os X Yosemite..??

[iMore Question]

I have kept windows 7 as my main OS. Whenever i open my Macbook and try to press option(Alt) button for opening my os X Yosemite then also windows 7 will start. What should i do to open my os X Yosemite..??

 

[kch50428]

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