In the manner of dictators, Mao suddenly summoned the two Americans to his private residence in the sequestered Chungnanhai compound next to the Forbidden City.

When a 90-year-old yellowed clipping appeared one day at my feet, an implausible new mystery entered my life.

Walls waited for him cunningly within the square blotch of darkness which the dormer's casement framed; if he passed himself within the casement the frame would enlarge into walls about him, trappingly, […]

In all the others, the design in one of the elements is moving clockwise while the one in the other element moves anticlockwisely but in (a), the design is moving anticlockwise in both the elements.