Please use the following link to view the journal article in order to answer the following question:

https://doi.org/10.1556/2006.4.2015.010

(PLEASE MAKE SURE YOU VIEWING THE CORRECT ARTICLE BEFORE ANSWERING CALLED:

Relationship of smartphone use severity with sleep quality, depression, and anxiety in university students BY KAD?R DEM?RC?*, MEHMET AKGNL and ABDULLAH AKPINAR)

Question:

There is no "true" independent variable in this study, because it is cross-sectional and correlational. However, the researchers clearly imply that there is a certain direction of causation between variables. What is the implicit "independent" variable in this study? 0 Smartphone Addiction 0 Depression Level 0 Anxiety Level 0 Sleep Quality