Answer:
k = 5
Explanation:
When a certain number 
 is multiplied by a scale factor
 is multiplied by a scale factor 
 , the final number is given by
, the final number is given by

and the final number will be:
- Larger than the original number if 

- Smaller than the original number if 

In this problem, the number 
 represents the size of the decoration.
 represents the size of the decoration.
If we apply the 4 scale factors given, we have:
- If 
 , then
, then 
 : this means that the final decoration is larger than the original decoration --> this is the correct option
: this means that the final decoration is larger than the original decoration --> this is the correct option
- If 
 , then
, then 
 : so the final decoration has same size as the original decoration
: so the final decoration has same size as the original decoration
- If 
 , then
, then 
 : so the final decoration is smaller than the original decoration
: so the final decoration is smaller than the original decoration
- If 
 , then
, then 
 , so the final decoration is smaller and inverted
, so the final decoration is smaller and inverted