Read the sentence. The essay is composed of three parts introduction, body, and conclusion.

How should the underlined part of the sentence (parts introduction,) be punctuated?
A parts, introduction
B parts: introduction
C parts; introduction
D parts-introduction

i decided to stay late in the laboratory to continue my experiment with the lightbulb. at midnight, thomas edison opened the door and walked in with his head held high.

1. he leaned on the wall and observed me carefully.

2. his harsh scrutiny made me self-conscious of my skills in the lab.

3. perhaps it was just me, but the air in the laboratory began to thicken as i found myself having difficulty to breathe.

4. i turned to look at him fully as i mentally prepared myself for what my very first words would be to thomas edison.

5. the next couple of seconds shocked me. it wasn't me who spoke, but rather him and with diction i could never think of using in a simple sentence.

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hey, sorry if this was bad, i really didn't know what to write but i wanted to you. is there anything that you had to include within the excerpt?

rising action   i think i did this not sure

the anwser is b because his violence took on the form