Final answer:
The number of students registered for the dodgeball tournament this year is 77.
Step-by-step explanation:
To find the number of students registered for the dodgeball tournament this year, we need to calculate the decrease in the number of students from last year.
First, we calculate the decrease in the number of students from last year:
Decrease = 23% of 100 = (23/100) * 100 = 23
Next, we subtract the decrease from last year's number of students to find the number of students registered this year:
Number of students this year = 100 - 23 = 77
Therefore, the correct answer is a) 77 students.