They have not caught the thieves change into passive voice

It was Sunday so I didn’t have to go to school. I woke up late, got up and WENT to the kitchen.
It was strange but I COULDN’T find our cat, Tom, anywhere. The whole family got worried.
“He’s gone hunting,” my YOUNGER sister said. 
“All cats hunt MICE. I read about it in a book.”
“I’m sure he IS SLEEPING in the armchair,” Mum said. But the cat wasn’t there either.
“Look! I HAVE FOUND him!” my little sister shouted. “He’s in the washing machine!” We watched in surprise as the cat got out of the washing machine.
“Come on, kitty, come here. We WILL  GIVE you some milk.”

Once professor Higgins (23) was called in the morning and told that his aunt had been taken to the hospital. As he had (24) to go to her at once, he drove  to school, went into the classroom and wrote on the chalkboard:  "Professor Higgins is (25) unable to have his classes today". There were several boys in the classroom, and one of them came (26) up and erased letter "c". He wanted (27) to make everybody (28) laugh But the teacher disliked such jokes. He took the duster and cleaned (29) away letter "l". The boys came running to look at the (30) sentence Nobody to be blamed but themselves!