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: 

1. An Apple Wireless Keyboard is paired to my Mac, but it doesn't help.
2. System has been restarted several times, doesn't help.
3. 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.
4. The Option key is fine, I have tested it by shortcuts like Command-Optiono-H which works.