Menu items from OpenCV examples not showing on android-onCreateOptionsMenu

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I'm running OpenCV examples on OpenCV 3.0 library, Eclipse Mars and Android target version 21. However, the menu items do not appear on my Android device. The relevant warning message is: Description Resource Path Location Type Invalid project path: Include path not found (C:\opencv\android-ndk-r10e\sources\cxx-stl\gnu-libstdc++\4.6\include). OpenCV Sample - face-detection pathentry Path Entry Problem

How can I solve this issue?-thanks