some structure problem

1. The Mississippi riverboat, which [I][U]evolved[/U][/I] from
simpler [I][U]steamship[/U][/I] of the early 1800's, became
the[I][U] dominant [/U][/I]form of [I][U]passenger transport [/U][/I]on
the Mississippi River.

2  Stars provided early [U][I]astronomer[/I][/U] with [U][I]a reference[/I][/U]
system [I][U]for[/U][/I] measuring [U][I]the motions [/I][/U]of planets, the
Moon, and the Sun.

3. The coal industry is important to [I][U]every[/U][/I] industrial
nations [I][U]because[/U][/I] most [I][U]other[/U][/I] industries are directly or indirectly [I][U]dependent[/U][/I] on it.

4. The [I][U]brightly [/U][/I]colored kingfisher [I][U]that perches[/U][/I] until it sights a fish, then dives into [I][U]the water[/U][/I]
to catch [I][U]its [/U][/I]prey.

5. Atoms are held together[I][U] by the [/U][/I]electrical forces
  [I][U] of [/U][/I]attraction between each negative electron and
  [I][U] a positive [/U][/I]protons [I][U]within[/U][/I] the nucleus.
6. Copper was the first[I][U] metal used[/U][/I] by
humans and is second [U][I]only[/I][/U] to iron
[I][U]into[/U][/I] its utility through [I][U]the ages[/U][/I].
7.The Hopi, [I][U]descendants [/U][/I]of the [I][U]prehistoric[/U][/I] Anasazi
people, are[I][U] a[/U][/I] Pueblo[I][U] people who [/U][/I]of the southwestern United States.