Based on the current action of North Korea,Do you think US should or should not take military action against N.Korea?

Not. When you're the biggest kid in the school yard, you don't flinch when some pissant starts talking smack. But if he's stupid enough to throw a punch, you block him and put him down quickly, decisively, and with overwhelming force.

Plus, China has a defense treaty with North Korea, meaning if the US attacks North Korea, even if preemptively, China will defend North Korea. China has reiterated that commitment, but in that same breath, China said to Kim Jong-un in front of the entire world that if North Korea attacks the US or any of the US's allies, China will NOT defend North Korea, and China is North Korea's only ally. North Korea hasn't had an alliance with Russia since 1992 when Russia cut off all aid to North Korea after the fall of the Soviet Union and North Korea immediately abandoned communism for Juche, a cult of personality that deifies the Kim dynasty and in which capitalism, private ownership, and civil self-reliance are the tenets rather than civil government reliance via Marxism. Since the US clearly doesn't want a war with China, the US then would be even more wise to stay its hand and let North Korea come at it if that is what Kim Jong-un is stupid enough to choose to do.

Of course not. way to late and it is not America that is at stake it is South Korea and Japan. If military action should have been taken it would have been under GWs regime but even that risked nuclear war with China. The only action that should be taken is diplomatic, either that or grant North Korea an NBA franchise.

What action deserves a military strike? They tested missiles.

I think if Kim continues to test ICBMs and nukes, we should blow one of them out of the sky. That would be taking defensive measures to a military action in my opinion.

The North Koreans have been pushing the envelope pretty hard, but have not stepped over the line (yet). An open war would almost certainly lead to the North Koreans using some of their nuclear devices. While it is not likely they could actually deliver one to the Continental US, South Korea and (probably) Japan would lose some cities and suffer millions of casualties. An open conflict (war) is NOT desirable IF it can be avoided.

I would like to see North Korea neutralised, preferably given to South Korean for unifying into one nation.

Rhetoric is meaningless. They haven't actually done anything.

Pity Trump hasn't a clue about international diplomacy.

No. This is China's backyard. If the US attacked North Korea, the North Koreans would retaliate and fire missiles and heavy artillery at South Korea. China would probably mobilize troops on the China North Korean border.

No, it would be foolish to do so except in retaliation for a direct attack by North Korea. The Chinese have said they will support the NKs if they are attacked, but if they launch the first attack they are on their own.

They should not.