What does Ambassador Muccio mean by “all out offensive"?
o North Koreans have crossed the neutral
zone.
South Koreans have crossed the neutral
zone.
North Korea has officially declared war on the
South.
South Korea has officially declared war on
the North

North Korea has officially declared war on the South.

Explanation:

When Ambassador Muccio says that there is an “all out offensive", he meant that North Korea has officially declared war on the South.

John J. Muccio was a U. S Ambassador to the Republic of Korea and coincidentally was the first ever. He was in the thick of the Korean war and when he said that there was an all out offensive, North Korea had just started hostilities with the South.

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.