1. The correct answer is D. semicolon.
When you are quoting somebody's words directly, there are some punctuation marks that go within the quote itself, and some which go outside of it. Those which you would write within the quote are period, question mark, comma, exclamation mark, and others, and those you would write outside of it are semicolon, dash, slash, etc.
2. The sentence which is written in the passive voice is D. The effects of cyanide are well known.
A passive sentence is a type of a sentence where the object is the focus. It is something that a particular action is done on - in this case, facts about cyanide are known. All other options here are active, meaning that the subject is the focus of the sentence, unlike in sentence D.
11. The correct answer is C. You're generating words that suggest possible sentences or paragraphs.
Webbing is a technique you use to generate some words that you might use in your essay to develop sentences and ideas. You write one word, and then branch it out to many others in order to help you develop your arguments. All other options here refer to brainstorming rather than webbing.
14. The correct answer is D. To own a word, write it over and over again.
It is important to write many different contexts and examples of where a particular word can be used in order to remember its meaning and usage. This is the appropriate connection between speaking (you will start using this word more and more in speech) and writing (the more you write it, the easier it will be to remember).
16. When writing, you can most effectively use a dash to B. get the reader's attention.
Dashes obviously cannot replace an exclamation point - that point is there for a reason, to show us that there is an exclamation taking place. An em dash, but not a regular dash can replace a semicolon, so C is also incorrect. Dashes don't really contribute to the formality of a sentence, so D is incorrect as well.