Finding the perimeter

This task is about the different perimeters of same-sized shapes.
 
five shapes on a grid
 
On the squared paper above, five different shapes, each made up of 6 unit squares, have been shaded in.
 
a)
Which shape has the smallest perimeter?
 
__________
 
b)
Which shape has the greatest perimeter?
 
__________ 
 
c)
On the squared paper above, draw two shapes each of 9 square units, one with a perimeter of 12 units, and the second with a perimeter of 20 units.
 
d)
Complete the statement:
 
If several figures have an area of 9 squares, the shape which is _____________________ has the least perimeter.