Inveed "3" sign seen in -

Answer is 'c' i.e. Ca head of pancreas "Ca of the head of the pancreas frequently causes changes in the duodenal loop. There may be widening of the duodenal loop, a double contour, irregularity of the inner border, and stricturing or distoion of the valvulae conniventes. The reversed '3' sign of Frostberg is often quoted as being characteristic, but is an infrequent finding." - Grainger