1. Weak: German, Chinese, Spanish, Russian, French, Latin, and Greek are all studied at Hotchkiss.
Better: At Hotchkiss, students study German, Chinese, Spanish, Russian, French, Latin, and Greek.
Explanation: The active version of the verb allows the sentence to show who's doing the studying. It also creates a livelier read.
2. Weak: Henry Louis Gates Jr. was arrested going into his own home.
Better: Sgt. James Crowley arrested Henry Louis Gates Jr, while the later was going into his own home.
Explanation: The active form of the verb allows the writer to assign agency to the person who committed this racist act.
3. Weak: The intent of the passage is seen in the author's use of the raft symbol.
Better: Twain's use of the raft as a symbol shows the instability of Huck's new non-racist outlook.
Explanation: Is seen doesn't say who sees what. The corrected version gives much more useful information.
4. Weak: The lake can be viewed from most of the classrooms in the English Wing.
Better: Students, teachers, and visitors to the school can see the lake from most of the classrooms in the English Wing.
Explanation: The active verb form allows the writer to say who is staring out the window during class.