The line from Helen Grey, which implies that the author thinks Helen's behavior is going to hurt herself is this: DON'T CUT YOUR FINGER WITH THE EDGE OF YOUR KEEN WIT.
Cutting one's finger implies hurting oneself or doing harm to oneself. When a man is said to have a keen wit, that means that, that man has a very sharp intelligence. So in the line given above, what the line is saying essentially is that 'Helen should not hurt herself with her sharp intelligence'.
The sentence that uses correct puntuation is, "I agreed with the speaker; as a result, I clapped very loudly when the speech was over."
A semi-colon is used after speaker to separate two ides and to avoid a run-on sentence. A comma should always be used after a transitional phrase, such as a result, likewise, finally, etc...
a. Is
b. University
c. Sophomore
d. At
B. Reciting
C. Reading
D. Surveying
D-participial: “tourists”
Ducking under an awning, the heavy rain caught me without a coat or an umbrella.
Ducking under an awning, I was caught without a coat or an umbrella in the heavy rain.