For a sentence to be complete, it must have a subject and a verb. Giving the incomplete sentence the missing parts will make it complete.
For example:
- "Went to the park" can be made complete by adding a subject to make it "We went to the park"
- "It blue" can be made complete by adding a verb to make it "It is blue"
- "The moon tonight" can be made complete by adding a subject and a verb to make it "I looked at the moon tonight"