11. He said he didn't know what was happening.
12. He said he was cutting off the main valve.
13. She said she would write him a prescription.
14. They said they were going to the drugstore.
15. She said she went to the supermarket every day.
16. Mary said she would like to speak to Susan.

11. He said, “I don’t know what is happening.”

=> He said he didn't know what is happening

12. He said, “I’m cutting off the main valve.”

=> He said he was cutting off the main valve

13. She said, “I’ll write him a prescription.”

=> She said she would write him a prescription

14. They said, “We’re going to the drugstore.”

=> They said they were going to the drugstore

15. She said, “I go to the supermarket every day.”

=> She said she went to the supermaket every day

16. “I’d like to speak to Susan,” said Mary,