Uses of this that these and those

C. FILL THE BLANKS WITH 'THIS', 'THAT', 'THOSE' AND 'THESE': (Use notepads to write)
1_______ was the most difficult case for Ravi ever. There was no way to tell who did it. A house key was left on an empty plate in the kitchen. There were cookie crumbs around the plate.2_______ were the only clues that Ravi had.
When you have a case like that, it takes a genius to solve it. Later, Ravi found cricket balls in the garden.3_________balls opened the case wide for Ravi. The balls belonged to Ravi's brother, Raju.4_________ meant the keys were Raju's. Raju had come home from school first and eaten the cookies. The mystery was solved. 5__________Was progress! But Ravi was still hungry. 6________ were, indeed, difficult times for Ravi.