When the Zen priest Murata Shuko declared, “The moon is not pleasing unless partially obscured by a cloud,” what was he referencing?

a) wabi, or qualities of austerity and the effects of time
b) chanoyu, or the ascetic discipline of the Buddhist tea ceremony
c) yugen, or spiritual profundity related to the action of a Noh play
d) tenshu, or a defensible refuge of last resort

Answer: a