Downwind for 1 miles，alter to starboard 90 degrees，go down this course for 1 mile；Then alter 90 degrees to starboard and go down this course for 2 miles；Then alter 90 degrees to starboard and go down this course for 2 miles；Keep adding 1 mile ever time you alter to starboard．This operation is（）search pattern

A.Williamson Turn

B.Parallel

C.Sector

D.Expanded