Option D:
is the correct answer.
Explanation:
Option A: 
The number 9.7 is multiplied with a certain number which results in the expression 
Thus, the expression is not equivalent to "9.7 split into a certain number of equal parts".
Hence, Option A is not the correct answer.
Option B: 
The number 9.7 is added with a certain number which results in the expression 
Thus, the expression is not equivalent to "9.7 split into a certain number of equal parts".
Hence, Option B is not the correct answer.
Option C: 
The number 9.7 is subtracted from the certain number n which results in the expression 
Thus, the expression is not equivalent to "9.7 split into a certain number of equal parts".
Hence, Option C is not the correct answer.
Option D: 
The number 9.7 is divided the certain number n which results in the expression 
Thus, the expression is equivalent to "9.7 split into a certain number of equal parts".
Hence, Option D is the correct answer.