Answer:
1: An act was performed by the elephants
2: A letter was written by my boss yesterday
3: The cure for the sickness was founded by her
4: The bone was found by the dog
5: The letter was signed by him today
6: They had sent him a message
7: They had spoken Spanish at the store
8: The sidewalk in being repaired by the city
9: The theif was sentenced by the judge
10: The explanation given by her had confused the students
11: While on the freeway, the police had stopped him
12: In the morning, she had opened the door
13: Last night, she had wrote the letter
14: She had cleaned the house
15: Was the new worker employed by the company?
16: Millions of people had visited the museum
Some of these are not the best, sorry!!
Step-by-step explanation: