question: If a single crab sits on a sediment surface in the image on the right.
#1 return crab 
#2 return surface 
#3 return #2 that is sediment 
#4 return #1 on #3 
#5 return #4 in  right image 
#6 return the  number of  #5 
#7 return if  #6 is equal to  one