The most appropriate word to complete the sentence "There were three boats on the ..................." is:
c. river
So the complete sentence would be: "There were three boats on the river."
The most appropriate word to fill in the blank, given the context provided in the sentence, is:
a. boring
So the complete sentence would read: "This film is very boring! Can we go out and play football?"
The best choice to fill in the blank is:
a. famous
So, the completed sentence would be: "Ronaldo and Messi are famous soccer players. Everyone in the world knows them."