Answer:
c. Make the message more formal, remove the personal discussion, and give more specifics about the survey plan.
Step-by-step explanation:
When writing a business related mail always focus on relevant information needed by the other party to accomplish a job, or to be informed about a situation.
In the mail that was written, there was a lot of personal content like.
Thanks for the lunch. I had a great time, and we accomplished a lot. Those pictures of your kids are adorable.
This sounds informal.
So as there is the possibility of the mail getting to your supervisor, the informal parts should be removed and specifics of the survey plan should be given.