Communication Systems: JEE Main 2011 Physics question

This question has Statement - $1$ and Statement - $2$. Of the four choices given after the statements, choose the one that best describes the two statements. Statement -$1$ : Sky wave signals are used for long distance radio communication. These signals are in general, less stable then ground wave signals. Statement -$2$ : The state of ionosphere varies from hour to hour, day to day and season to season.