| |||
afield (谱); aporia; conundrum; dilemma; floorer; Gordian knot; puzzler; quandary; spinosity; sticker; stickler; stumper; teaser; toughie; toughy | |||
problem | |||
crux | |||
difficult problem; hard nut; staggerer | |||
troublesome problem | |||
challenge | |||
hard nut to crack | |||
roadblock | |||
staggering problem | |||
bottleneck | |||
knotty problem; thorny problem; thorny subject | |||
hot potato; puzzle; quiz | |||
| |||
tickler; twister; twistor | |||
| |||
poser | |||
| |||
crux | |||
| |||
quaestio vexata | |||
| |||
knot |
难题 : 71 phrases in 22 subjects |