Read the passage.
with my backpack full of notes about my essay and borrowed books, i trudged through the slush to the library. after months of note-taking, i was eager to compose my thesis. the library’s fourth floor housed a computer lab, and i could hear the hum of fifty computers as i exited the elevator. unfortunately, there were no available computers, and among the political posters on the wall, a makeshift list had been added for people awaiting a turn at a computer. i added my name to the list and considered returning to the typewriter in my dorm room.
what can readers infer about the time period of the passage?
textbooks were too expensive for students to afford.
college students were expected to publish their writing.
college libraries were gathering places for student activists.
personal computers were not the norm among students.

Personal computers were not the norm among students.

Explanation:

Based on the information provided in the passage we can infer that personal computers were not very common at that time. First of all, the student has a backpack full of notes and books from the library, that means his main source of information were those books and the only way to take notes was by writting them in paper. Nowadays most of students take notes in their laptops and have the texts in them too.

We can argue that the reason of that is that the student didn't have enough money to buy a laptop so he used a computer from the library. But when he arrived to the computer lab it was full with students in his same situation. Therefore none of those students had a personal computer and needed to go to the library to finish their homework. In conclusion, personal computers were not common for the average student.

type of error:

the error in the sentence is a "dangling modifier". a dangling modifier is a phrase, word or clause that "dangles" because there is not target to modify. in this case, "after mopping the floor" is the dangling modifier since it has no word to modify. the noun "house" cannot mop the floor; therefore there is a mistake in the writing of the sentence.

answer; i believe the correct and best answer is (a crime motivated by prejudice); ///good luck