Final answer:
The word used to specify that a procedure is recommended in FAA Order 7110.65 is 'should'. So, the correct answer is option c.
Step-by-step explanation:
The word used to specify that a procedure is recommended in FAA Order 7110.65 is should.
When the word should is used, it indicates that a procedure is recommended but not mandatory.
For example, in the context of air traffic control, the phrase 'Pilots should maintain a continuous listening watch' means that it is advisable for pilots to always be listening to radio communications while flying. So, the correct answer is option c.