It is the 9th century.
899AD was the last year of the 9th century.
72AD was in the 1st century AD.
The year 705 AD is in the 7th century.
1150 AD is in the 12th century.
4 AD is in the 1st century. The 1st century spans from the year 1 AD to the year 100 AD. Therefore, 4 AD falls within this timeframe.
899AD was the last year of the 9th century.
800-899 AD, methinks. It is probably mostly recognized that the 9th century runs from 800-899. However, since there was no Year 0, the second century did not rightfully start until the year 101. So the 9th century is technically comprised of the years 801-900. Just as the 21st century did not technically start until 2001.
There were two: The 9th century BCE (commonly thought of as BC) was 900-801 BCE. The 9th century CE (commonly thought of as AD) was 801-900 AD. Now, many will tell you that the century begins with the zero year (100, 1000, etc.). Not so. Consider that when you count to ten, you start with one, not zero (as in 1-2-3-4-5-6-7-8-9-10); the same is true with calendars.
King Alfred the Great.
We are currently in the 21st century, thus the 8th century was 701-799. (Although some would dispute the first year as you imply, it is common to take the year xx1 rather than xx0.)
1st century AD
The first century AD.
The 3rd Century AD.
It is the first century AD.
The 1st century AD.
The 1st century AD.
It is the first century AD.