A snail, climbing a 20 feet high wall, climbs up 4 feet on the first day but slides down 2 feet on the second. It climbs 4 feet on the third day and slides down again 2 feet on the fourth day. If this pattern continues, how many days will it take the snail to reach the top of the wall?
Choose the most appropriate option:
A) 12  B) 16  C) 17  D) 20  E) 21
total transaction in two days = 4-2= 
<gadget id="calculator">4-2</gadget>
<output>2</output>
2 feet   in 16 days it will climb 16 feet   on the 17th day , the snail will climb 4 feet , thus reaching the top   therefore , total no of days required=17   ANSWER:17
<result>C</result>
A snail, climbing a 20 feet high wall, climbs up 4 feet on the first day but slides down 2 feet on the second. It climbs 4 feet on the third day and slides down again 2 feet on the fourth day. If this pattern continues, how many days will it take the snail to reach the top of the wall?