疑難問題

knotty problem / intractable difficulty

to doubt / to suspect

hard to understand / difficult to deal with / knotty / complicated

difficult (to...) / problem / difficulty / difficult / not good

disaster / distress / to scold

to ask / to inquire

to ask; to inquire

question / problem / issue / topic / CL:個|个[ge4]

surname Ti

topic / problem for discussion / exam question / subject / to inscribe / to mention / CL:個|个[ge4],道[dao4]