What is the most widely used operating system for personal computers

Eye injuries usually occur as a result of all of the following things, except: a) proper machine operation b) battery explosion c) falling or flying debris d) electric welding arc

Idon understand these and need some ! ?

Which best describes the role or restriction enzymes in the analysis of edna a. to break dna into fragments that vary in size so they can be sorted and analyzed b. to amplify small amounts of dna and generate large amounts of dna for analysis c. to purify samples of dna obtained from the environment so they can be analyzed d. to sort different sizes of dna fragments into a banding pattern that can be analyzed