Option-Left/Right Arrow doesn't work The keyboard shortcuts Option-Left/Right Arrow is made for moving the cursor by words, as Apple described here: https://support.apple.com/en-us/HT201236 , but doesn't work on my MacBook Pro (15-inch, Mid 2010, OS X 10.11). They fail to work everywhere I can try, including but not limited to Notes, TextEdit, Mail, Google.com search field and iMessage text field. Meanwhile on my friend's MacBook Air (13-inch, Mid 2013, OS X 10.11), they work damn well! Anyone can help?

Note: 


An Apple Wireless Keyboard is paired to my Mac, but it doesn't help.
System has been restarted several times, doesn't help.
Including Option-Delete and Option-Shift-Up Arrow, all the Option related shortcuts in the "Document shortcuts" session of https://support.apple.com/en-us/HT201236 doesn't work.
The Option key is fine, I have tested it by shortcuts like Command-Optiono-H which works.
The problem has been solved by switching the input source from "Unicode Hex Input" (my major input source) to "U.S.". I think some option based shortcuts can't function as usual with "Unicode Hex Input". You can update the input sources by searching "unicode" to be directed to system preferences -> Keyboard. Click "Input Sources" and remove other input methods that might be causing the error. Then open a new window for the program you want to test.