For employee training, the employee-to-instructor ratio is 18 to 2. If there are 36 instructors for the training, how many employees participated in the training?

A. 540
B. 216
C. 432
D. 324

The employee-to-instructor ratio is 18 to 2, which simplifies to 9 to 1. This means that for every 1 instructor, there are 9 employees. If there are 36 instructors, then there are 36*9 = <<36*9=324>>324 employees.

Therefore, the answer is D. 324.