Which or that [restrictive clauses ]

Paok alway read your q's 'cause they make me think
A rare occurrence

'Which' vaguely implies there might be only one such; but otherwise, let's hope we hear from Cen or the like

Otherwise 'which' seems a bit awkward, dounno why


Not that it matters, but I mighta writ,

North Korea as a rogue nation has become a great threat and embarrassment to China, which is trying to help but with little success.

http://www.business-standard.com/article/current-affairs/north-korea-great-threat-and-embarrassment-to-china-donald-trump-117090300586_1.html

http://thehill.com/homenews/administration/338622-trump-china-tried-to-help-with-n-korea-but-it-has-not-worked-out

North Korea as a rogue nation has become a great threat and embarrassment to China, which is nevertheless trying to help ease tensions arising from its recent nuclear test; but with little success

In British English, "which" is often used interchangeably with the restrictive "that". This common British construction is not strictly incorrect in American English, but it is generally avoided, especially in formal writing.

Thanks Cen, I feel acquitted