A frog fell into a drain that was 20 cm deep. After one hour, it mastered enough  energy to make a jump of 6 cm but it then slid down 4 cm. If it continued in this  pattern every hour, how many hours in total will it take to get out of the drain? 
选项为:A:$$5$$  B:$$6$$  C:$$7$$  D:$$8$$  请回答其中一个选项.