a can of worms
複雑で解決困難な問題
a castle invulnerable to attack
難攻不落の城
a catalog of disasters [misfortunes]
災難［不運］の連続
a challenging course
難しいコース［科目］
a counsel of perfection
((形式))完璧かんぺきだが実行困難な助言
a [the] crown of thorns
イバラの冠；苦難
a difficult age
（１０代の）難しい年頃
a difficult childbirth
難産
a difficult [hard] choice
難しい選択
a difficult decision (to make)
困難な決定
